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K.F. WENDT LIBRARY

UW COLLEGE OF ENGR.

215 N.RANDALL AVENUE

MADISON Wl 53706

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K.F. WENDT LIBRARY

UW COLLEGE OF ENGR.

215 N.RANDALL AVENUE

MADISON Wl 53706

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^S'-

.^'.

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INTERNATIONAL
LIBRARY OF TECHNOLOGY

A SERIES OF TEXTBOOKS FOR PERSONS ENGAGED IN THE ENGINEERING

PROFESSIONS AND TRADES OR FOR THOSE WHO DESIRE

INFORMATION CONCERNING THEM. FULLY ILLUSTRATED

AND CONTAINING NUMEROUS PRACTICAL

EXAMPLES AND THEIR SOLUTIONS

AUTOMOBILE-ENGINE AUXILIARIES

AUTOMOBILE CARBURETERS

ELECTRIC IGNITION

TRANSMISSION AND CONTROL MECHANISM

BEARINGS AND LUBRICATION

AUTOMOBILE TIRES

(VOL. I)

SCRANTON:
INTERNATIONAL TEXTBOOK COMPANY

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Atitomobile-Ensiiie Auxiliaries: Copyri&rht. 1910. by International Tbxtbook
Company. Entered at Stationers' Hall, London.

Automobile Carbureters: Copyrisrht. 1907. 1910. by International Textbook
Company. Entered at Stationers' Hall. London.

Electric Isrnition. Parts 1 and 3: Copyright, 1907. 1910, by International Text-
book Company. Entered at Stationers' Hall, London.

Electric Ifimition. Part 2: Copyrisrht. 1910, by International Textbook Com-
pany. Entered at Stationers' Hall, London.

Transmission and Control Mechanism: Copyrisrht. 1910. by International Text-
book Company. Entered at Stationers' Hall, London.

Bearinars and Lubrication: Copyrigrht, 1907. 1910. by International Textbook
Company. Entered at Stationers' Hall. London.

Automobile Tires: Copyrisrht. 1910, by International Textbook Company.
Entered at Stationers' Hall, London.

All risrhts reserved.

Printed in the United States.

<^S^ 21000

110

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14978G

JAN 2 11^11

PREFACE

The International Library of Technology is the outgrowth
of a large and increasing demand that has arisen for the
Reference Libraries of the International Correspondence
Schools on the part of those who are not students of the
Schools. As the volumes composing this Library are all
printed from the same plates used in printing the Reference
Libraries above mentioned, a few words are necessary
regarding the scope and purpose of the instruction imparted
to the students of — and the class of students taught by —
these Schools, in order to afford a clear understanding of
their salient and unique features.

The only requirement for admission to any of the courses
offered by the International Correspondence Schools, is that
the applicant shall be able to read the English language and
to write it sufficiently well to make his written answers to
the questions asked him intelligible. Each course is com-
plete in itself, and no textbooks are required other than
those prepared by the Schools for the particular course
selected. The students themselves are from every class,
trade, and profession and from every country; they are,
almost without exception, busily engaged in some vocation,
and can spare but little time for study, and that usually
outside of their regular working hours. The information
desired is such as can be immediately applied in practice, so
that the student may be enabled to exchange his present
vocation for a more congenial one, or to rise to a higher level
in the one he now pursues. Furthermore, he wishes to
obtain a good working knowledge of the subjects treated in
the shortest time and in the most direct manner possible.

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iv PREFACE

In meeting these requirements, we have produced a set of
books that in many respects, and particularly in the general
plan followed, are absolutely unique. In the majority of
subjects treated the knowledge of mathematics required is
limited to the simplest principles of arithmetic and mensu-
ration, and in no case is any greater knowledge of mathe-
matics needed than the simplest elementary principles of
algebra, geometry, and trigonometry, with a thorough,
practical acquaintance with the use of the logarithmic table.
To effect this result, derivations of rules and formulas are
omitted, but thorough and complete instructions are given
regarding how, when, and under what circumstances any
particular rule, formula, or process should be applied ; and
whenever possible one or more examples, such as would be
likely to arise in actual practice — together with their solu-
tions — are given to illustrate and explain its application.

In preparing these textbooks, it has been our constant
endeavor to view the matter from the student's standpoint,
and to try and anticipate everything that would cause him
trouble. The utmost pains have been taken to avoid and
correct any and all ambiguous expressions — both those due
to faulty rhetoric and those due to insufficiency of statement
or explanation. As the best way to make a statement,
explanation, or description clear is to give a picture or a
diagram in connection with it, illustrations have been used
almost without limit. The illustrations have in all cases
been adapted to the requirements of the text, and projec-
tions and sections or outline, partially shaded, or full-shaded
perspectives have been used, according to which will best
produce the desired results. Half-tones have been used
rather sparingly, except in those cases where the general
effect is desired rather than the actual details.

It is obvious that books prepared along the lines men-
tioned must not only be clear and concise beyond anything
heretofore attempted, but they must also possess unequaled
value for reference purposes. They not only give the maxi-
mum of information in a minimum space, but this infor-
mation is so ingeniously arranged and correlated, and the

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PREFACE V

indexes are so full and complete, that it can at once be
made available to the reader. The numerous examples and
explanatory remarks, together with the absence of long
demonstrations and abstruse mathematical calculations, are
of great assistance in helping one to select the proper for-
mula, method, or process and in teaching him how and
when it should be used.

This and the succeeding volume are devoted to the prin-
ciples of operation and details of construction of gasoline
automobile mechanism. The first volume is devoted to an
exposition of the principles of operation and characteristic
features of construction of cooling and muffling devices,
carbureters, ignition apparatus, transmission and control
mechanism, lubricating devices, and tires. Tire deterioration
and methods of making temporary and permanent tire repairs
are thoroughly and clearly explained. The second volume
deals with the relations that the parts of the gasoline auto-
mobile bear to one another in the assembled vehicle; the
principle of operation and details of construction of two-cycle
and four-cycle automobile engines; use of throttle and spark
levers for regulating the speed of a running automobile;
directions for starting the engine and car under all conditions;
adjustment and care of carbureters, spark-coil and magneto-
ignition devices, valves, brakes, friction clutches, planetary
and sliding-gear transmissions, wheel bearings, chains, uni-
versal joints, steering gears, springs, and lamps; road rules
and customs; ignition troubles of every kind; carbureter dis-
turbances; engine starting and running difficulties; cylinder
and piston disorders; valve derangements; lubricating and
cooling-system troubles; overhauling and repairs, involving
the inspection, adjustment, and renewal of different elements
of the running gear and power plant. The two volumes will
fully meet the needs of any person who wants to know how
to operate, care for, and maintain a gasoline automobile,
whether as a chauffeur or owner, and whether or not such per-
son already has an ordinary knowledge of automobile run-
ning. The text was written by experts, and imparts a correct
and intimate knowledge of the principles involved in the

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vi PREFACE

construction, maintenance, and handling of modem gasoline
automobiles.

The method of numbering the pages, cuts, articles, etc. is
such that each subject or part, when the .subject is divided
into two or more parts, is complete in itself; hence, in order
to make the index intelligible, it was necessary to give each
subject or part a number. This number is placed at the top
of each page, on the headline, opposite the page number;
and to distinguish it from the page number it is preceded by
the printer*s section mark (§). Consequently, a reference
such as § 16, page 26, will be readily found by looking along
the inside edges of the headlines until § 16 is found, and
then through § 16 until page 26 is found.

International Textbook Company

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CONTENTS

Automobile-Engine Auxiliaries Section Page

Cooling Systems 4 1

Exhaust Mufflers 4 24

Starting Devices 4 29

Governing Devices 4 34

Automobile Carbureters

Combustible Mixtures 5 1

Gasoline Supply Tanks 5 15

Types of Automobile Carbureters .... 5 19

Carbureter Construction 5 28

Carbureter Connections 5 49

Carbureter Regulation and Adjustment .5 51

Electric Ignition

Elementary Principles 6 1

Magnets and Magnetism 6 12

Electromagnetic Induction 6 18

Batteries 6 20

Spark Coils 6 41

Sparking Appliances 7 1

Current-Measuring Instruments .... 7 28

Ignition Systems 7 34

Direct-Current Generators 8 1

Magneto-Electric Generators 8 19

Low-Tension Magneto Systems 8 36

Dual Ignition Systems 8 42

High-Tension Magnetos 8 45

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vi CONTENTS

Transmission and Control Mechanism Section Page

Clutches 9 1

Speed-Changing Mechanism 9 20

Power Transmission to Driving Wheels 9 39

Steering Mechanisms 9 46

Brake Mechanism 9 55

Bearings and Lubrication

Types of Bearings 10 1

Systems of Lubrication 10 17

Lubricating Devices 10 19

Automobile Oils 10 34

Automobile Tires

Types of Tires 11 1

Tire Maintenance 11 .20

Tire Deterioration 11 34

Roadside Tire Repairs 11 40

Vulcanized Tire Repairs 11 59

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AUTOMOBILE-ENGINE AUXILIARIES

COOLING AND MUFFLING DEVICES

COOIiING 8Y8TEM8

INTRODUCTION

1. In an intemal-combustion engine, unless provision
were made for cooling, the heat from the explosion of the
charge would raise the temperature of the cylinder walls and
piston so high as to render lubrication impossible. The
devices employed for cooling purposes comprise what is known
as the cooling: system of the automobile.

Many automobile engines are cooled by circulating water
or some other liquid through the space between the outer
wall of the cylinder and a jacket casing that surrounds the
cylinder head and the part of the cylinder barrel nearest the
head. Air is used for cooling in only a comparatively small
proportion of automobile engines, and in some cases oil is
used in winter as the cooling medium.

About the only objection to the use of water for cooling is
that it is liable to freeze in cold weather. In order to over-
come this objection, various substances are added to the
water or dissolved in it so as to form a mixture that will not
freeze until the temperature is considerably below that at
which pure or nearly pure water freezes.

2. The method of cooling with liquids is the same for all
liquids. When water is used for cooling, it enters the jacket

COPTRIOHTtO BT INTKRNATIONAL TEXTBOOK COMPANY. KNTIRCO AT STATIONER*' HALL. LONDON

222—2

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§ 4 AUTOMOBILE-ENGINE AUXILIARIES 3

space generally either at its lowest part, or just below the
exhaust valve, and flows out at the highest part. It is
extremely important to have the water flow from the highest
part of the jacket space, because an air pocket or steam
pocket would be formed if a portion of the enclosed space
were higher than the outlet. It is also very important that
the jacket space should be shaped so that there is no part
from which the water cannot flow upwards toward the outlet.
It is not necessary, however, that the circulating water should
enter the jacket at the extreme lowest portion; in some
engines that give the best of service, the water enters just
beneath the exhaust port.

The hot water from the jacket passes through connecting
pipes to a radiator, where it is cooled, and from the radiator
it passes back to the jacket space of the engine again. It
then repeats its cycle of cooling the engine and being cooled
in the radiator. Circulation is maintained either by a pump,
which forces the water through the system, and which on this
account is called a forced circulation system, or by what is
known as thermal circulation, which means circulation due to
the heating of the water.

WATER COOLING

3. Water-CooIlng Systems. — In Fig. 1 is shown the
arrangement of the parts of a typical cooling system for
automobiles with vertical engines located at the forward part
of the car. The water passes from the tops of the cylinders c,
as indicated by the arrows, to the top of the radiator 6, down-
wards through the radiator, and from the bottom of the latter
to the mechanically driven circulating pump a. This pump
forces the water through the pipe that rises vertically above
it and then across horizontally to the water-jackets of the
four cylinders. The pipe leading to the bottom of the jacket
spaces branches, so that the water divides and part flows
through each jacket space. In high-power cars, there are
often two connections between the pump and the bottom of
the radiator. In this particular instance, the carbureter d
is water-jacketed. A small amount of water taken from one

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AUTOMOBILE-ENGINE AUXILIARIES

§4

of the cylinder jackets circulates through the carbureter
jacket to warm the carbureter, and the water passes on to the
bottom of the radiator, where it mixes with the other water
as it goes to the pump.

4. A tliepino, or tlierinal, system of circulating the
cooling water, sometimes called a thermo-siphon system, is
shown diagrammatically in Fig. 2. The radiator for cooling is
shown at a. The top b of the radiator is connected to the top
of the jacket spaces by a pipe that rises from the engine
cylinders d. The bottom c of the radiator is connected to
the bottom of the jacket space. Circulation depends on the

Fio. 2

fact that water, when heated, is lighter per unit volume, as
per cubic inch, quart, etc., than water at a lower temperature.
The water becomes heated in the jackets around the cylinders,
and is therefore lighter than the water in the radiator. This
condition causes the water to rise from the jackets and to
flow through the connecting pipes to the top of the radiator.
At the same time the heavier water in the radiator settles
down and causes flow from the bottom of the radiator to the
bottom of the jacket. The continuous heating of the water
around the cylinder maintains this circulation while the
engine is operated. In general, heating the water tends to
make it flow upwards; cooling it tends to make it descend.

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J 4 AUTOMOBILE-ENGINE AUXILIARIES 5

The top b of the radiator is shown in the form of a tank in
the illustration. The object of the tank is to supply enough
water to allow for small leakage and evaporation. In many
automobiles, this tank occupies a comparatively small space
above the upper ends of the cooling tubes of the radiator.

The level of the water in the tank located above the
radiator must always be above the bottom of the opening
to which the pipe leading from the tops of the water-jackets
is connected. In order to maintain a circulation by thermal
action, there must be a connection between the water in the
tank and that in the inclined pipe. If the water falls below
the bottom of the opening at the upper end of the inclined
pipe, circulation will stop.

5. Certain undesirable features are piu^posely shown in
Fig. 2. One of these is that the bottom of the radiator is
below the bottom of the jacket space around the cylinders.
If the water becomes cooler as it flows from the radiator to
the engine, as is generally the case, the water flowing upwards
from the horizontal pipe will more than counterbalance an
equal height of water in the lower part of the radiator. This
produces a tendency to counteract circulation in the desired
direction. The extent of this counteracting influence is
proportional to the distance that the horizontal pipe is below
the bottom of the jacket space. The best arrangement is to
have the bottom of the radiator somewhat higher than the
bottom of the jacket space, so that the water can flow down-
wards from the radiator to the jackets.

Another undesirable feature is that the opening through
which the water from the engine enters the tank b of the
radiator is located above the bottom of the tank. Under
such conditions, the circulation will stop as soon as the level
of the water falls below the bottom of the opening, even if a
considerable amount of water is still retained in the tank
and the upper ends of the cooling tubes a are covered with
water to a considerable depth. The proper place to connect
the inflow pipe is at the bottom of the tank. Its opening
will then be covered as long as the tank contains any water.

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AUTOMOBILE-ENGINE AUXILIARIES

§4

There should be no vertical (up or down) bends — at least
none of any great extent — in the connections between the
bottom of the radiator and the water-jacket. Such bends tend
to form pockets in which cool water will settle and thus
impede circulation. In some cases, vertical bends may pre-
vent the beginning of circulation entirely, especially when the
engine is first started after having cooled down. Vertical
bends in the hot-water pipe also tend to check the circulation
in a thermal system.

6. A thermal cooling system used only on the cars of one
manufacturer is shown diagrammatically in Fig. 3. In this

system the hot water enters the radiator some distance below
the top. It first passes upwards through part of the tubes,
and then downwards through the remaining tubes to the
bottom of the radiator.

The radiator a has two pockets b and c into which flows the
hot water from the engine. The water rises from these
pockets through the two groups of short cooling tubes d and e
to the top of the radiator, and then descends through another
group of short cooling tubes / to a horizontal pocket, or

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AUTOMOBILE-ENGINE AUXILIARIES

header, g that extends across the radiator from side to side.
The water then descends through a large group of cooling
tubes h to the bottom i of the radiator, from which place it

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flows through a pipe to the lower part of the jacket around the
engine cylinder. The tops of the upper sets of cooling tubes
must be kept covered with water in the space /; if they are

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8 AUTOMOBILE-ENGINE AUXILIARIES § 4

not covered in this manner, the circulation will cease. This
cooling system operates with entire success.

7. In all cases, the cooling system should not be air-tight,
but should have an orifice above the normal level of the
water to allow the escape of air, water, or steam. The water
expands by heating, and in case it boils, steam is formed.

8. Types of Radiators. — Radiators are usually
made of thin metal, with as much surface exposed to the air
as possible, and they are arranged so that the air can circu-
late through them easily. Four forms of radiators are shown
in Fig. 4.

The first. Fig. 4 (a), consists simply of a zigzag coil of cop-
per tubing, on which are soldered a large number of thin fins
that increase the surface available for contact with the air.

The radiator shown in Fig. 4 (6), although similar to that
shown in Fig. 4 (a), is more complete, in that it has headers
at the ends to which the flanged tubes are connected. The
whole arrangement is enclosed in a sheet-metal casing having
the outline of the automobile front.

The radiator shown in Fig. 4 (c) consists essentially of top
and bottom headers connected by a large number of thin,
flat tubes that are crimped into zigzag shapes and placed
vertically as close together as possible. In this way the water
is divided into a large number of thin sheets contained in
tubes with thin metal walls, through which the heat of the
water passes rapidly to the air drawn between the tubes
by the speed of the vehicle, aided usually by a suction fan
just behind the radiator.

Fig. 4 (d) shows the back view of a type of radiator that
consists of a shell with front and back tube plates into which
are connected a large number of small horizontal tubes.
The water inside the radiator surrounds the tubes, and the
air that does the cooling passes through them. The fan a
aids in the circulation of the air. It is held in place by the
three braces 6, c, and d. The water enters the radiator at
the upper right-hand comer through the connection ^, and
leaves through the opening / at the lower left-hand comer.

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§4

AUTOMOBILE-ENGINE AUXILIARIES

The forms of radiators shown in Fig. 4 (a) and (d) are
virtually obsolete, and are found only in old cars.

9. Fig. 5 illustrates a radiator of much the same form
as that shown in Fig. 4 (c). The chief difference is that the
thin, flat, vertical copper water tubes are straight, instead of
crimped, as in the latter figure. Another difference is that

Fig. 5

the straight vertical tubes in Fig. 5 have fins. Each fin is a
continuous piece extending from side to side of tlie radiator
and has a perforation for each vertical water tube. The
water tubes end at the headers, one at the top and the other
at the bottom.

10. A sectional radiator is illustrated in Fig. 6, in which
two of the sections are shown separately. Each section

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AUTOMOBILE-ENGINE AUXILIARIES

§4

extends across from side to side of the radiator, and its depth,
made up of several horizontal tubes, extends from the front
to the back of the radiator. The construction is such that the
sections can be removed incjividually for repairs if necessary.

11. In Fig. 7 (a) is shown what is commonly called a
bLoneycomb radiator, and often spoken of as being of the
Mercedes type. This radiator is composed of a large number

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of small square tubes about 4 inches long. The ends of each
tube are enlarged, and they are nested, as shown in Fig. 7 (6) .
After assembling, the enlarged ends of the tubes are soldered
together. The water circulates through the narrow spaces
between the tubes. In some radiators of the honeycomb
type, hexagonal tubes with enlarged ends are employed, in
which case the resemblance to a honeycomb is very marked.

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§4

AUTOMOBILE-ENGINE AUXILIARIES

12. Circulation in Radiators.— The circulation of
water through a radiator is generally from the top to the bot-

tom. This is the natural direction of flow of the water,
because the hot water, which enters at the top, becomes

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AUTOMOBILE-ENGINE AUXILIARIES

§4

heavier as it cools and therefore has a tendency to flow to the
bottom of the radiator. There are modifications of this
method of circulation, however, even when no pump is used
to force the water through the system. In such cases, heat
alone is depended on to produce the circulation of the water.
A system of this kind was described in Art. 6. In the case of
radiators of the form shown in Fig. 4 (a), it is common to find
a circulating pump forcing water into the bottom of the
radiator and out at the top, or in a direction contrary to that
in which gravity would cause the water to flow.

The outer surface of radiator tubes is usually given a dull-
black color in order to increase the cooling effect of the air

that comes in contact with it.
This black surface is some-
times secured by chemical
means and at other times by
painting.

13. Circulating
Piimpa. — All pumps used
on automobiles for circulating
the cooling water are prob-
ably of the rotary type, as
distinguished from the recip-
rocating, or plunger, type.
There are two general types
of rotary pumps, namely,

the centrifugal and the positive^ or fixed-volume- per ^revolution,

type.

14. In Fig. 8 is shown a ceiitrifujjral pump. This
pump has a rotor a that is rigidly fastened to the shaft b that
drives it, and consists of a disk, on one side of which are
vanes c — eight in number in this case. The rotor is com-
pletely enclosed in a case, except at the inlet and the outlet!
part of the casing being shown in the figure. The free edge
of each vane fits fairly close against the inlet side of the case,
which is not shown in the figure. The circular inlet is indi-
cated by the dotted circle d. When the direction of rotation

Fio. 8

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§4

AUTOMOBILE-ENGINE AUXILIA^RIES

is as indicated by the arrow, the rotor carries the water around
and discharges it from the outlet e, provided the passage out-
side the pump is open. The discharge of water is due to both
the centrifugal action and the peripheral velocity of the water
in the pump. If the passage external to the pump is closed,
the water in the pump will only be whirled around with the
rotor. The pressure will not be much greater under this
condition than when the pump is discharging at a moderate
rate; it never becomes high enough to injure any properly
constructed part.

The quantity of water or oil that the pump will discharge
per minute is in a measure proportional to the size, orresist-

FiG. 9

ance, of the external passage for a given speed. The quan-
tity increases as the speed increases. The bearing through
which the driving shaft enters the casing has a stufiingbox
that is packed with fibrous packing to prevent leakage.

Water-circulating pumps of this type may be driven at the
same speed as the crank shaft of the engine. It is not unusual,
however, to drive the pump at the speed of the cam-shaft
of a four-cycle engine, or half the speed of the crank-shaft.
A centrifugal pump of the form just described will continue to

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14 AUTOMOBILE-ENGINE AUXILIARIES § 4

give fair service even after the parts are considerably worn.
A loose fit between the edges of the vanes and the casing will
allow some of the water ta flow back toward the center of the
pump, however, and the eddy currents thus set up will cause
a loss of efliciency. By placing a disk on each side, or edge,
of the vanes, so that the vanes are between the disks and
connected to them, the wearing surface can be made more
durable. , In such a pump, the hub must be partly hollow to
admit water between the inner ends of the vanes. In cheap
centrifugal pumps, the vanes project from the hub without a
disk on either side of them. This is the least durable and
efficient form of vane centrifugal pump.

Although the centrifugal type of pump is used chiefly on an
automobile for circulating the cooling water, it is used to a
small extent for circulating lubricating oil.

15. In Fig. 9 is shown a gear-pubap that is used
to some extent for circulating either cooling water or lubrica-
ting oil. It consists of a pair of ordinary spur gears a enclosed
in a case having intake and outlet openings b and c opposite
each other. One gear is driven by a shaft and transmits
motion to its mate by means of the intermeshing teeth. The
directions of rotation of the gears and the divided path of the
liquid are indicated by arrows. The teeth of the gears fit
closely together so as to prevent any flow of liquid between
them. The ends of the gears fit snugly against the casing.

A pump of this type delivers the same amount of liquid per
revolution, whether the speed and pressure are high or low.
If a stoppage occurs in the pipes of a pump that is closely
fitted, the pressure will increase between the discharge side
of the pump and the stoppage until either the pump ceases
to operate or something breaks. Such a pump, however, soon
wears so as to have enough leakage between the gears and the
casing to prevent the formation of pressure high enough to
cause breakage of ordinarily strong parts. When used to
circulate oil, there is naturally not much wear, because the
bath of oil thoroughly lubricates the moving parts. This
gear-pump operates equally well in both directions.

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16. Another type of gear-pump is illustrated in Fig. 10.
The engine drives the rotating member a, which in turn
drives the other
member. The direc-
tion of rotation is
indicated by the
arrows. The water
enters at b and passes
out at c, being carried
around by the teeth d
and e. The sides and
tips of the teeth of
the rotating members
of this pump contain
grooves that, it is
claimed, prevent to p>° *o

a large extent leakage past the teeth and thereby increase the
efficiency of the pump.

17. The type of circulating ptunp shown in Fig. 11 con-
sists of a cylindrical barrel a that revolves eccentrically in a
chamber b. The shaft on which the barrel a turns is central
with a, and the water is moved by two blades c and d that are
pressed outwards by a spring e. The action of the pump

PlO. 11

depends on the motion of the blades c and d in the chamber b.
Suppose the barrel a to be in the position shown and rotating

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in the direction of the arrow until the blade d has covered the
edge / of the intake port; the water in front of the blade d
will then be driven before it and out through the port g.
Meanwhile, as soon as the blade d has covered the edge /,
water is drawn into the space h behind the blade d until it
has nearly reached the position of the blade c. This operation
is repeated by the two blades, thus producing an almost con-
tinuous flow of water.

18. circulation Pressure GaujE^e. — In order that the
operator of an automobile may know whether or not the
cooling water is circulating properly, a pressure $cau$ce

such as is shown in Fig. 12 is
sometimes placed in the piping
circuit. The gauge, which is
frequently styled a telltale, is
usually attached to the dash in
such a position that it may
readily be seen. The pressure
created by the p,ump and regis-
tered by the gauge in ounces
per square inch gives some idea
as to the velocity with which the
water is passing through the cir-
culating system. If the gauge
fails to register, it is evident
that no water is flowing through the piping.

19. Cold-Weather Cooling lilquids. — If a car is to

be used in very cold weather, it is advisable to fill the cooling
system with some liquid that will not readily freeze. In
weather not colder than 10° F. above zero, especially if a
wind is blowing, it requires only a short time for water to
freeze in the radiator if the engine is stopped out of doors,
as in the case of a breakdown. The freezing may be pre-
vented for a considerable time, however, by covering the
radiator with a blanket or a robe.

Commercially pure mineral oil, and various non-freezing
mixtures are used in cold weather. Some of these mixtures

Fig. 12

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act on rubber in such a way as to soften it, and others may
attack some of the metals of the cooling system, especially
if an impure chemical is used. None of these solutions is
very satisfactory. In fact, most of them require rapid motion
by a circulating pump in order to cool the car sufficiently if
the weather becomes warm.

Of the mineral oils, probably the grade used in refrigerating
plants is best for cooling, as it will remain liquid at low
temperatures. The water should be entirely drained out
before putting oil into a cooling system, and the oil should
fill the system completely, just the same as when water is
used. As an inflammable vapor is given off by the oil when

TABLE I
FREEZING POINT OF AL.COnOI>-AND- WATER MIXTURES

Percentage of
Wood Alcohol

Pecentage of
Water

Freezing Point of Mixture
Degrees F.

18 above zero

5 above zero

2 above zero

.70

9 below zero

15 below zero

30 below zero

it is hot, a lighted match or candle should not be used to see
whether there is sufficient oil in the system. The oil should be
completely removed before water is again put in the cooling
system.

20. If wood alcohol is mixed with water, it will lower
the freezing point. Table I gives the approximate freezing
temperatures for various proportions of the alcohol and water.

The wood alcohol vaporizes and passes out of the cooling
system more rapidly than does the water. It is therefore
necessary in order to maintain the proper proportions to add
more alcohol than fresh water. The vapor of alcohol is
inflammable. Some experiments seem to show that the
222—8

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18 AUTOMOBILE-ENGINE AUXILIARIES § 4

cooling system can be closed so as to have no outlet through
which the alcohol vapor can escape. A safe way to close the
vent pipe is to tie a piece of rubber tubing or sheet rubber over
the end of the pipe so that the rubber will give way should the
pressure in the cooling system become higher than is safe.
Wood alcohol will not injure either rubber or metal.

21. Calcium chloride (not chloride of lime) dissolved in
water forms a solution that will not freeze so rapidly as water
alone. Only chemically pure chloride should be used, how-
ever. The impurities in ordinary commercial calcium
chloride are apt to attack some of the metals or alloys of the

TABLE II

FRBBZIKG POINT OP CAIXJIUM^HLORIDE-AND-WATER
MIXTURES

Calcium Chloride per Gallon
of Water
Pounds

Freezing Point
Degrees F.

I.O

27.0 above zero

2.0

18.0 above zero

3.0

1.5 above zero

3-5

8.0 below zero

4.0

17.0 below zero

S.o

30.0 below zero

cooling system, especially zinc and solder. Table II gives
the approximate freezing points of various proportions of
calcium chloride and water.

22. Glycerine and water also form a mixture that stays
liqxiid at a lower temperature than water alone. The glycer-
ine, however, attacks and destroys the rubber in hose connec-
tions, etc. Instead of using a mixture of just these two
liqmds, wood alcohol is often added. The glycerine is liable
to deposit on the walls of the cooling system if the cooling
mixture becomes very hot. Table III gives the approximate
freezing points of various mixtures of this kind.

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23. If water alone is used for cooling during cold weather,
it should be drained off completely when the car is left stand-
ing in a cold place overnight. It should be seen that no
water remains in any pocket from which the water cannot
drain as the radiator empties. Although nearly all modern
cooling systems will drain perfectly by gravity upon opening
a drain cock located at the lowest point of the system, many
of the older cooling systems will not. Some of these systems
cannot be emptied perfectly except by applying air pressure
to the highest point. If available, compressed air from a
storage tank should be used for this purpose ; otherwise, blow-

TABIiE III

FREEZING POINT OF MIXTURES OF GLYCERINE, WOOD
ALCOHOL, AND WATER

Percentage of
Glycerine

Percentage of
Wood Alcohol

5-0

Percentage of
Water

Freezing Point
Degrees F.

5-0

25 above zero

lo.o

lO.O

15 above zero

12.5

8 above zero

15.0

150

5 below zero

12.0

25.0

10 below zero

25.0

50.0

20 below zero

ing into the system with the mouth or using a tire air pump
will do. It is almost impossible to drain radiators of the form
shown in Fig.. 4 (a) without applying air under pressure.

AIR' COOLING

24. In order that a cylinder may be cooled sufficiently
with air to keep its temperature down to a working limit,
it is necessary to provide a greater radiating surface with
which the air can come into contact than is presented to the
atmosphere by a cylinder having a smooth exterior. The
increased radiating surface is secured by placing projections

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§ 4 AUTOMOBILE-ENGINE AUXILIARIES 21

on the parts of the cylinder that need the most cooling. These
projections are generally in the form of fins, lugs, or pins.
The fin is ordinarily made up in the form of a thin, flat ring
whose inner edge is in intimate contact with the cylinder
casting or forms an integral part of it. Wlien pins are used,
each pin sometimes has one end screwed into a tapped hole
in the cylinder wall so that it stands out radially from the
cylinder; or, each pin has one end cast into the cylinder, so
as to hold it in position.

Under normal conditions of operation, the air-cooled engine
runs much hotter than one cooled by water or some other
liqmd. It is not unusual for an air-cooled engine to become
hot enough at the cylinder head and exhaust port to glow in
the dark. Engines of this class have operated successfully
for long periods at this high temperature. However, unless
the fuel supply can be completely cut off, difficulty is some-
times met in stopping engines when they are so hot. The
maximum size at which an air-cooled automobile engine can
be operated seems to be about 8 or 10 horsepower per cylinder.

25. The usual method of bringing air into contact with
the radiating surfaces of the cylinders consists in blowing
air against them by means of a rotary fan.

In another method, the parts with which the air is to be
brought into contact are enclosed in a casing and a current
of air is either forced through or drawn through the casing by
means of a fan. A greater amount of air can be brought
into contact with the radiating surfaces in this manner than
when they are not enclosed by a casing.

Fig. 13 shows the assembly, and Fig. 14 one cylinder, of
an automobile engine that is air-cooled by this method.
Fig. 15 shows a cylinder in several stages of assembly.
Like parts have been given the same reference letter in the
three figures.

A centrifugal blower a is placed at the front end of the
engine and run by gears at about three and one-half times the
speed of the engine, forcing a strong blast of air under a pres-
sure of about 2 ounces per square inch to the head of each

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cylinder and downwards around the cylinder walls. The
inlet and exhaust valves work horizontally, opening into a
small valve chamber 6, Fig. 14, at the extreme top of the
cylinder head. They are opened by bell-cranks c and push
rods d. Fig. 14. As indicated in Fig. 15, the cylinder walls
are studded externally with small pins cast on the cylinder.
Around each cylinder is a light aluminum housing e. Figs.
13 to 15, that holds the air stream close to the cylinders.
The housings are open at their lower ends, and at their upper
ends connect with an air pipe /, Fig. 13, that conveys the air
from the blower. The air pipe is of tapering cross-section.

Fig. 15

the small end being that farthest from the blower. The spark
plugs s. Figs. 13 and 15, screw into the extreme top of the
cylinder heads and project upwards into the air pipe, which
keeps them cool.^ The electrical connections for the spark
plugs are carried through the air pipe. With this method
of cooling, from 70 to 80 cubic feet of air per minute per
horsepower is required.

26, A perspective view of the cooling system of a well-
known automobile using air cooling is shown in Fig. 16.
Some of the parts are cut away, however, so as to show the
construction clearly. In this system, a metallic case formed

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21 AUTOMOBILE-ENGINE AUXILIARIES § 4

by the box a, the sod pan 6, and the side frames c, surrounds
the engine. Set into the top of the box a are sheet-metal
cylinders d. These cylinders are open at the top and the
bottom and surround for the greater part of their length the
vertical cooling flanges of the cylinders. Cold air entering
through the grilled front of the bonnet e is drawn through the
cylinders d, past the cooling flanges, and is delivered to the
rear by a suction-fan fl)rwheel /, thus doing away with the
use of a separate fan.

In this cooling system/ the cold air meets the hottest part
of each cylinder, and in descending, it tends to equalize the
temperature at all points of the cylinders.

KXHAU8T MUFFIiEUS

PUBP08E OF MUFFLING

27. Gases exhausting unrestricted from the cylinder of an
internal-combustion engine pass into the atmosphere at such
a high velocity, especially at high engine speeds, that the
result is a continuous noise that can be likened to a series of
sharp detonations. This noisy exhausting of the gases is
decidedly objectionable, and for this reason many efforts
have been made by inventors to produce a device that will
muifle the detonations to a degree that will render them
unobjectionable. The device used for this purpose is called
an exliaust muffler.

Generally speaking, the exhaust may be muffled by leading
the exhaust gases into a chamber, or chambers, where they
can expand to a low pressure and cool at the same time.
In most mufflers, the single large stream of exhaust gases
coming from each cylinder is broken up into numerous small
streams, or thin sheets, to insure rapid cooling and reduction
in velocity. In some mufflers, the cooled exhaust gases are
discharged into the atmosphere in a scries of fine streams,
and in others, especially the most modern mufflers, the dis-
charge is in a single stream. It is now the common practice

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either to plax^e a valve of some suitable form between the
muffler and the engine, or to incorporate a valve directly
with the muffler, the valve being operated by a conveniently
located foot-pedal. This valve, known as the muffler cut-
out, opens directly to the atmosphere, and when open, it
allows the engine to exhaust directly into the air, either for
testing the regularity of the explosions or to gain a slight
increase of power by eliminating the back pressure created
by the muffler.

A good muffler, in effectively, muffling the sound of the
escaping exhaust gases, will not create an excessive back pres-
sure on the engine.

CONSTRUCTION OF MUFFLERS

28. Fig. 17 illustrates in section a typical modern exhaust
muffler of the type that breaks up the exhaust gases into
numerous fine streams. It has two cast-iron heads a and 6,
and four concentric cylindrical shells c, d, e, and / that are held
in position by grooves in the two heads. The assembly is
held together by long bolts that pass through both heads.
The exhaust pipe g is attached to the head a and discharges

Fig. 17

into the inside of the shell c. The gases pass through small
perforations at the left end of the shell c into the larger
shell d, expanding in doing so, because the volume of
the shell d is much larger than that of the shell c. The gases
in the shell d pass through perforations at the right end of this
shell and expand into the shell e. They then pass through
holes in the left end of the shell e into the outer shell /, expand-
ing therein and, finally, they escape into the atmosphere

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through the nozzle h. This type of mufHer has a cut-out valve ♦
fitted into the head b. This valve is opened by pulling on a
cable attached to the cut-out lever ;, when the exhaust gases

Fig. 18

can pass from the exhaust pipe g through the inside shell c and
the openings in the valve seat of i into the atmosphere.

29. A modem exhaust muffler of the type that breaks
the solid stream of exhaust gases into thin sheets is shown
disassembled in Fig. 18. It has an outer shell a that is closed
when assembled by the heads b and c. The head b is fitted
with a cut-out valve d, and to this head is connected the
exhaust pipe. Placed inside of the shell a is a series of cones
e and /. The cones e are closed at the apex and the cones /
have the apex open; that is, they are really frustums of cones.

■y*

Fio. 19

These sheet-metal cones are held in place by three supporting
shafts g and tubular distance pieces h. The exhaust gases
entering the muffler strike the first closed cone e and pass over

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§ 4 AUTOMOBILE-ENGINE AUXILIARIES 27

its inside surface up to its edge; they then pass over the out-
side surface into the cone /, which delivers the gases into the
inside of the second closed cone e, and so on. The gases
finally escape through a passage in the head c into a tube and
thence into the atmosphere.

30. Fig. 19 illustrates, in longitudinal and end cross-
section, a muffler of the type that breaks the exhaust gases into
numerous small streams. In this form of muffler there are six
cylindrical steel shells, three of which are placed eccentric to
the center of the muffler. The exhaust gases enter the
central chamber a of the muffler, and pass through perfora-
tions at the top to the first expansion chamber formed by the
annular space between the first and second shells. The gases
pass through perforations in the bottom of the second shell
into the second expansion chamber, and leave this through
perforations in the top of the third shell, entering the third
expansion chamber, and so on. The gases finally leave the
muffler through the exhaust port h and pass into the
atmosphere.

31 • Mufflers are liable to fill gradually with soot (loose
carbon). For this reason, they should be taken apart occa-
sionally and cleaned. When a muffler is apart, the shells
or cones, especially those which first receive the exhaust
gases, should be examined for corrosion. If a cut-out valve
is incorporated in the muffler, it also should be cleaned and
examined, and, if necessiiry, repair should be made.

MUFFLER CUT-OUTS

32. Although many cars are fitted with a muffler cut-out,
there are some that are not provided with this device. To
meet the demand of owners who desire to place a muffler cut-
out on the exhaust pipe, numerous cut-out devices have been
placed on the market. Some of them can be applied with
very little labor.

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33. Fig. 20 illustrates a form of muffler cut-out that will
open automatically if an explosion occurs in the muffler, thus

acting as a safety
valve. It consists of
a T-shaped body a
that is threaded in-
ternally at b and c to
fit threads cut on the
exhaust pipe. At d
is formed a valve seat
that is normally
closed by the valve e,
which is held to its
seat by a spring /.
'A light wire cable is
attached to the lever
g. When this cable
is pulled in the direction shown by the arrow, the valve e
is pushed away from its seat d and a direct passage to the
atmosphere is provided for the exhaust gases. If at any

Fig. 20

Fig. 21

time the pressure in the exhaust pipe is great enough to
overcome the tension of the spring /, the valve c will auto-
matically open outwards.

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34. The form of muffler cut-out illustrated in Fig. 21
is intended to be clamped to the exhaust pipe after cutting
into this pipe a V-shaped notch. For this purpose the body a
is made in halves. The cut-out valve fc, which is a butterfly
valve, is fastened to the shaft c. This shaft also carries the
crank d that serves to turn the valve b. This valve is shown
in its open position.

STARTING AND GOVERNING DEVICES

STARTING 1>EVICE8

HAND STARTERS

35. The common method of starting an internal-com-
bustion automobile engine consists in turning the crank-
shaft by hand until a charge is drawn into the cylinder and
is compressed and ignited. For this purpose, a hand crank
that can be temporarily con-
nected to the crank-shaft is
used. This hand crank is
always so constructed that
it will automatically disen-
gage from the crank-shaft as
soon as the engine starts.

36. In starting an inter-
nal-combustion engine, the
spark should be retarded, so
as to prevent firing before
the expansion, or power,
stroke begins. If the spark
is not suflBciently retarded,
the explosion will occur before the compression stroke is
completed, and the crank-shaft will rotate backwards, and
the sudden pressure thrown on the crank-handle by the too
early explosion of the charge will give it a severe backward
jerk that is liable to injure the operator.

Pig. 22

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To prevent backward rotation of the crank-shaft due to
failure to retard the spark, some automobile manufacturers fit
them with a safety device that prevents the engine from being
cranked until the spark has been retarded.

37. Fig. 22 illustrates diagrammatically a safety starting
device applied to a vertical engine located under the hood.

The starting crank a
is shown by dotted
lines in its disengaged
position. A spark-
retarding lever b is
fulcrumed at c, with
its lower forked end
resting against a col-
lar of the starting
crank. The upper
end of the lever b is
connected to the
timer d by means of
a chain. When the
starting crank is
pushed rearwards in-
to engagement with
the crank-shaft, the
upper end of the
b spark-retarding lever
is carried forwards,
rotating the timer so
as to retard the spark.
The relative positions
when the starting
crank is engaged is
Pio. 28 shown by the full lines.

38. In Fig. 23 is illustrated a safety starting device
suitable for an automobile fitted with a two-cylinder opposed
engine that is placed lengthwise under the body. In this
device, a safety cam a that swings on a pivot is connected to

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1 4 AUTOMOBILE-ENGINE AUXILIARIES 31

the spark lever by means of a rod actuated by the pin b. The
connection to the spark lever holds the cam in such a position
that it is interposed between the starting crank c and the end
of the crank-shaft, as shown in Fig/ 23 (a), except, of course,
when the spark lever is fully retarded. In that case, the
safety cam occupies the position shown in Fig. 23 (6), thus
permitting the starting crank to be pushed into engagement
with the crank-shaft.

AUTOMATIC STARTERS

39. The apparent advantage of being able to start an
internal-combustion automobile engine from the seat occupied
by the driver, and without great muscular effort on the part
of the driver, has led to the design of many automatic starting
devices. Very few of these devices, however, have an
extended use. Automatic starters ntiay be roughly divided
into spring-operated starters, pressure starters, and charging
starters.

Fig. 24

40. Springs-Operated Starters . — In springs-operated
starters, as a rule, the motion of the car or engine winds up
a spring, which, when released by a suitable trigger, spins
the engine crank-shaft in imitation of hand cranking.

Fig. 24 illustrates a spring-operated starter applied to a
driving shaft. This shaft is divided into two parts. The
forward part carries a drum inside of which is a heavy volute
spring, and the rear part carries the sliding member 6 of a
jaw clutch that can be made to engage mating jaws carri^
at the rear of the drum a. The sliding member b is thrown

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32 AUTOMOBILE-ENGINE AUXILIARIES § 4

in and out by a lever, not shown in the illustration, the lever
being operated by a wire attached to it. This wire terminates
in a knob placed on the dashboard.

The operation of the device is as follows: While the car
is running, the divided propeller shaft is locked together by
the jaw clutch, of which the part b is the sliding member.
To start the engine when the car is at rest, the high-speed
clutch is let in to couple the engine to the forward half of the
propeller shaft. The sliding member b is then moved to the
rear, when the spring acts and turns the engine crank-shaft
from 10 to 20 revolutions. To rewind the spring, the reverse
is thrown in and kept in until the machine backs. The
sliding member b is then slid forwards to lock the two halves
of the propeller shaft together, and the engine is declutched.'
The car is now ready to go ahead, and may be started in the
way usual when the engine is running.

41. Pressure Starters. — In pressure starters, gas

under pressure is stored in a tank, from which, by suit-
able means, it can be admitted to the different cylinders in
succession, thus rotating the crank-shaft until a charge
explodes.

To one make of six-cylinder car is fitted a pressure-operated
automatic starting device consisting of two end cylinders
connected by small pipes to a pressure tank placed below the
body. Some of the pressure of each explosion stroke passes
to this tank, which is thus filled with compressed gas. The
tank is connected by a pipe to a push-button valve located
on the dashboard, and from this valve the pipe leads the
compressed gas to a distributor valve driven by the engine.
This valve distributes the compressed gas to the different
cylinders in their regular firing order.

If it is desired to start the engine when the pressure tank
is filled with compressed gas, as shown by a pressure gauge on
the dashboard, the push-button valve is opened. The com-
pressed gas is then led by the distributor valve to whatever
oylinder is on the power stroke, thus starting rotation of the
crank-shaft. If for any reason the first cylinder in the firing

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order fails to fire, the distributor valve sends the compressed
gas to the cylinder next in the order of firing, and so on, if
necessary, through the series of cylinders. As soon as firing
occurs, the push-button valve is closed.

A separate shut-off valve is provided to prevent compressed
gas from escaping from the tank when the car is to remain
idle for any length of time.

Fig. 26

42. Chargringr Stoi-ters. — In char^ng^ starters, a

charge of gasoline vapor and air is forcibly injected into the
cylinders and ignited from a battery ignition system.

A charging-starter outfit is shown applied to a machine in
Fig. 25. As will be observed, a hand-operated air pump is
attached to the side of the car in a position convenient to the
operator. The cylinder a of the air pump is of large diameter,
and the piston rod b is provided with a handle c of convenient
size. The object of the pump is to compress air for starting,

222—4

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34 AUTOMOBILE-ENGINE AUXILIARIES § 4

the air passing over gasoline in the surface carbureter d on its
way to the valves e, through which the starting charge is
admitted to the cylinders. To start the engine, the valves e
and compression relief cocks / are opened by means of the
operating handle g attached to the rod A; the driver gives
the pump plunger a few strokes, and the air is driven through
the carbureter d to the explosion chambers of the engine cylin-
ders. The charge is then ignited and the engine thus started.
Air for the compressor is drawn into the pump cylinder a on
the upward stroke through the flap valve i, and is expelled on
the downward stroke through the outlet valve ;, which is
seated by a spring, as indicated. Simultaneous operation of
the relief cocks and charging valves is effected by connecting
the rods k and / to the lever m attached to the rod h.

GOVERNING DEVICES

HAND GOVERNING

43. Most automobile engines are controlled by manipula-
tion of the throttle valve and the position of the spark, some-
times called the spark lead. More accurately, the control
proper is accomplished by regulation of the throttle, and
the spark advance is regulated to keep the ignition at its
most advantageous point for developing the maximum power
of the charges received.

The manipulation of the spark alone is sometimes employed
to modify the speed of the engine, because, with the spark
retarded to cause ignition to occur later than it should, the
power of the engine is very materially reduced. This, how-
ever, is a most objectionable practice for several reasons:
In the first place, it evidently wastes gasoline, because the
same result as regards power may be obtained with smaller
charges and an earlier spark. Second, the inflammation is
so prolonged that it probably is not completed at the time
the exhaust valves open, so that the valve seats are exposed
to streams of gas still burning. This not only overheats

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§ 4 AUTOMOBILE-ENGINE AUXILIARIES 35

the valves and is liable to warp them, but it soon bums and
cuts their ground faces and their seats. Third, the engine is
overheated, and preignition of the incoming charge may
result, producing explosions in the carbureter and intake pipe.
It is, however, permissible to retard the spark to prevent
racing, that is, running too fast, when the throttle is nearly
closed and the engine is running light, with the car standing
still.

44. Since automobile engines are operated under wide
variations of speed and load, it follows that for correct action
the throttle and spark cannot always be operated together.
For example, a rarefied charge, such as is obtained with the
engine nmning at medium speed, with the throttle nearly
closed, will bum in a comparatively slow manner and requires
an advanced spark for its prompt combustion. Suppose,
now, that the car is nmning at moderate' speed under these
.conditions, as it may when descending a slight grade, or
even on level ground. If a slight up grade is encountered,
the operator will open the throttle to increase the power.
Under such conditions the speed of the engine will probably
not increase, but it will be found that the spark advance
suitable for the previous conditions is too early for the
increased charges. This will be indicated by the laboring
sound and possible pounding of the engine, either of which
sounds may be stopped at once by slightly retarding the
spark.

If the throttle and the spark mechanism were positively
connected, it would be impossible to advance the spark while
closing the throttle, as was required for the first set of con-
ditions, and to retard the spark while opening the throttle,
as was necessary for the second set of conditions. Although
having the two positively connected simplifies the operation
of the car in the hands of the novice, and although this
arrangement is undoubtedly satisfactory under some con-
ditions, as for example when the car is speeded along a level
road, it is not flexible enough to give the most favorable
results in either speed or fuel economy.

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AUTOMOBILE-ENGINE AUXILIARIES

§4

AUTOMATIC GOTEBNOR8

45. Automatic governors are used to some extent on
automobiles for controlling the speed of the engine so as to
prevent it from increasing above a predetermined maximum,
which maximum can generally be varied at the will of the
driver while running the car. The governors used are usually
of the jlyhall type, one form of which is shown in Fig. 26.

The flyballs a ro-
tate with the shaft h
on which they are
mounted. Their
tendency to fly out-
wards on account of
the rotation is re-
sisted by a pair of
coil springs, one of
which is shown at c.
An arm on each of the
flyballs engages with
the sleeve d, which is
free to slide along the
shaft 6. As the speed
of rotation of the
governor increases,
the flyballs move out-
wards and slide the
sleeve d toward the
right. This motion
of the sleeve carries
with it one end of
the shorter arm of a
bell-crank e, which is pivoted at /. The longer arm of the
bell-crank is therefore moved upwards, carrying with it the
rod g, which is connected to the throttle valve h in the mixture
inlet pipe i of the engine. The throttle is therefore closed
as the increased speed of the engine causes the flyballs to
move outwards.

Fig. 26

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§ 4 AUTOMOBILE-ENGINE AUXILIARIES 37

46. The governor may be constructed so that the flyballs
will move out gradually as the speed increases, and thus close
the throttle gradually; or, it may be constructed so that the
flyballs will not move outwards before the speed of rotation
has reached a certain value, and then move out very rapidly
with slight additional increase of speed. In the latter case,
the engine is allowed to receive full charges up to nearly the
limit of speed, and then the charges are cut down before the
speed in(5reases very much beyond this limit. The latter
method of operation is more suitable for an automobile
engine.

In automobile engines, the mechanism connecting the gov-
ernor to the throttle valve is generally provided with means
for adjusting it, so that the speed at which the governor acts
to cut off the fuel can be varied by placing the throttle lever
in different positions. The throttle lever can thus be set so
that the car will maintain a speed of say 15 miles an hour
over any ordinary road, or it can be set so as to maintain a
speed of say 30 miles an hour over the same road. Different
forms of mechanism are used to accomplish this method of
changing the speed at which the governor acts. The mecha-
nism used in most cases permits of throwing the governor out
of action, either to maintain a higher speed than that at which
the governor is set for the time, or to close the throttle so as
to stop the engine. In some cases, this is accomplished with-
out any direct controlling action on the governor itself, and
in other cases, which are not so desirable, the sleeve of the
governor is shifted by the throttle control against either
the resistance of the governor springs or the tendency of the
flyballs to move outwards, as the case may be.

The device for varying the controlling action of the gover-
nor or of suspending it altogether, so as to obtain increased
power when ascending hills, is called an accelerator, and is
usually operated by a foot-pedal near the steering column.

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AUTOMOBILE CARBURETERS

PRINCIPLES OF CARBURATION

COMBUSTIBIiE MIXTURES

DEFINITIONS

1. When a combustible vapor and air are mixed in proper
proportions and ignited, the combination of the gas with
the oxygen of the air is so rapid as to produce an explosion^
which may be defined as an extremely rapid combustion
accompanied by the formation of gases and increased pres-
sure. The sudden rise of pressure produced is made available
for driving internal-combustion engines, of which the auto-
mobile engine is one type.

2. Two or more elementary substances may be mixed
together and yet not combine to form a new substance.
They are then said to form a mixture. The mixture has
the properties of the elements composing it. The most
familiar example of a mixture is ordinary air. It is com-
posed of oxygen and nitrogen, 23 parts, by weight, of the
former to 77 parts, by weight, of the latter. The two gases
do not combine chemically; they are simply mixed.

A mixture of two or more substances whose chemical
combination will cause an explosion is called an explosive
mixture. An explosive mixture of gasoline vapor and
air is composed of the vapor of 1 part of liquid gasoline to
from 8,000 to 10,000 parts of air, by volume. The volume

COrTRIOHTCD BY INTERNATIONAL TEXTBOOK COMPANY. ENTERED AT •TATIONERS* HALL, LONDON

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2 AUTOMOBILE CARBURETERS § 5

of the vapor will vary, but an average proportion will be
2.15 parts of gasoline vapor to 100 parts of air.

The enriching of air, as by adding to it the vapor of gasoline,
naphtha, kerosene, alcohol, etc., is called carburatlon
of the air; the device used for carbureting the air is called a
carbureter. The mixture formed is variously called the
combustible mixture, the sras, or simply the mixture.

3. The operation of setting fire to the gaseous mixture
in the engine cylinder by means of a device called an igniter
or a spark plu|^ is known as ignition. The moment
that ignition begins is called the time of ignition. The
quantity of the mixture of gas and air taken into the cylinder
at one time is called the charge, and when all of it is
ignited, it is said to be wholly inflamed. The time elapsing
between the time of ignition and the moment when the gas
is wholly inflamed is known as the duration of inflamma-
tion or duration of the explosion. The velocity with which
the flame is generated in the charge is called the rale of
flame propagation,

COMBUSTION AND FUKL.8

4. The internal-combustion engine used on automobiles
bums the fuel inside the engine, as the name indicates. The
fuel used is generally either gasoline or naphtha; less fre-
quently, it is alcohol, and, in rare cases, kerosene. All these
fuels are liquids in the commercial form. The burning,
or combustion, of the fuel liberates heat, which is a form of
energy. The function of the engine is to convert some of
this heat energy into mechanical energy, which can be utilized
to perform the work of driving the car.

5. Combustion is a very rapid chemical combination.
The atoms of some of the elements have a very great affinity,
or attraction, for those of other elements, and when they
combine, they rush together with such rapidity and force
that heat and light are produced. Oxygen, for example,
has a great attraction for nearly all the other elements. An

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§ 5 AUTOMOBILE CARBURETERS 3

atom of oxygen is ready to combine with almost any sub-
stance with which it comes in contact. For carbon and
hydrogen, oxygen has a particular attraction, and whenever
these elements come in contact with oxygen at a sufficiently
high temperature, they combine with great rapidity. The
combustion in an automobile-engine cylinder is of this
nature. The temperature of a small portion of the mixture
of gas and air is raised by an electric spark, and then the
fuel charge begins to combine with oxygen taken from
the air. The combination is so rapid and violent that a
great quantity of heat is given out, and this heat suddenly
raises the temperature of the mixture. Combustion, therefore,
is the rapid chemical combination of two or more stibstances,
resulting in the production of heat.

6. When the affinity of two substances is not so great
as to make them spontaneously combustible, it is necessary
to start combustion by bringing some portion of the sub-
stances to the temperature of combustion. In the case of
gases or combustible vapors in automobile engines, the heat
for ignition is derived from an electric spark. The electric
spark, although very small, is of a very high temperature,
and is amply sufficient for the purpose, provided the propor-
tions of the two combustibles, or of the combustible and the
oxygen adjacent to the spark, are approximately those
required for chemical union. A strong spark, however,
will cause a more rapid spread of the flame than a weak spark.

7. Products of Combustion. — The gases produced by,
or remaining after, combustion in an automobile-engine
cylinder are known as the products of combustion, fre-
quently called the exbaust grases, or simply the exhaust.

All the fuel oils and gases are chemical compounds of
hydrogen and carbon, and are called hydrocarbons. When
burned in oxygen, they split up, the hydrogen and carbon
uniting separately with the oxygen in the air and producing
water vapor and carbon dioxide, respectively. When carbon
and oxygen combine, they form carbon dioxide ; when hydro-

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4 AUTOMOBILE CARBURETERS § 5

gen and oxygen combine, they form water. When, as is
ordinarily the case, the oxygen is obtained from the air, the
nitrogen of the air passes into the engine cyUnder along with
the oxygen. It takes no part in the combustion and passes
off through the exhaust with the carbon dioxide.

8. The gases produced by the combustion of any of the
combustible mixtures such as are herein mentioned contain
some steam as the result of the chemical combination that
takes place between the oxygen of the air and the combustible
elements of the fuel. There is ordinarily some moisture in
both the air and the gas or vapor, and this moisture is changed
into steam by the heat of combustion. If the gaseous
products are cooled to a temperature as low as that of the
atmosphere, the steam will condense into the form of water.

The heat of burning a gaseous combustible mixture increases
the volume of the gas if the pressure is kept constant, as
when the mixture is burned in the open air; but if the mixture
is confined in a closed space, so that the gases cannot expand
and increase their volume, the burning increases the pressure
against the walls of the enclosing vessel. As the gases cool
after burning at constant pressure, the volume contracts.
In the case of constant volume, the pressure falls as the
temperature decreases.

9. Gasoline. — Internal-combustion engines equipped
with carbureters use fuels composed of hydrogen and carbon.
Gasoline is in most general use, and its behavior is typical
of all fuels used in engines of this class. It is produced in
the early stages of the distillation of petroleum, and is a
mixture of various substances of different evaporative rates
depending on the extent to which the distillation is carried.
At one time, gasoUne was much cheaper than kerosene, and
the tendency of the refiner was to produce as small a propor-
tion of gasoline as possible from the crude oil ; in other words,
to market gasoline of high evaporative rate. The develop-
ment of this type of engine for automobile use, however,
has created a demand for gasoline that has raised its price
considerably, and the refiners now produce more gasoline

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§ 5 AUTOMOBILE CARBURETERS 5

from the same crude oils. As a result, the commercial gasoline
of today has a much lower evaporative rate than formerly,
and there is a tendency toward the production of still heavier
gasoline.

10. Gasoline is particularly adapted to use in modem
high-speed automobile engines on account of its high evapo-
rative rate at moderate temperatures, evaporation being an
essential to thorough mingling and complete combustion of
the charge in the limited time available. It is not, however,
a substance having a definite chemical composition, but a
mixture of various substances having different evaporative
rates. At low temperatures, certain of these substances are
not readily vaporized so as to give their maximum effect
in the engine. In fact, vaporization is sluggish at very
moderate temperatures, owing to the cooling effect of the
evaporative process on the inspired charge and on the car-
bureter and intake pipes. This is illustrated on starting a
cold engine in cold weather, when a considerable excess of
fuel makes starting easier. The excess is required because
only the lighter portions of the fuel are evaporated at that
temperature and are available for ignition, the heavier
portions being inert.

11. Quality of Gasoline. — Gasoline varies con-
siderably in quality; the lighter it is in weight, the more
volatile and better it is for use in automobile engines. It
should also be free from water. A poor quality of gasoline
makes it difficult to start an engine, especially when the
gasoline is cool. In fact, gasoline of poor quality has more
the nature of kerosene, which, of course, does not vaporize
readily, even at the temperatures of summer weather. A
good quality of gasoline, however, vaporizes readily at a
temperature as low, or even lower, than the freezing point of
water; that is, as low as 32° F.

12. Stale grasollne is the name quite frequently
applied to gasoline that does not vaporize readily. If a good
grade of gasoline is left standing in an open vessel, the more

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AUTOMOBILE CARBURETERS

§5

volatile, or lighter, portion of it will vaporize rapidly, leaving
the heavier, or less volatile, portion that constitutes stale
gasoline, which is of the same nature as a low grade of gasoline.
In the early history of the automobile, the standard quality
of gasoline was kept fairly close to that which was known
as 76^ gasoline. This designation of the quality comes from
the use of a Baum^ hydrometer to test the
specific gravity, or heaviness, of the gasoline.

13. In many parts of the United States, the
only available gasoline for automobiles is known
as stove grasoline, which has a specific gravity
of from 65° to 72*^ Baum6.

Low-grade gasoline can be used with satis-
faction after an engine is started, provided the
air that enters the carbureter is heated by being
drawn around the exhaust pipe or cylinders.
This is also true in the case of a carbureter that
is heated by the warm water of the cooling sys-
tem. A carbureter that is heated by a portion
of the exhaust gases of the engine passing through
a jacket around the carbureter will also operate
on a lower grade of gasoline with much better
satisfaction than an unjacketed carbureter when
the latter is used without preheating the air
that enters it.

Fio. 1 14. Testing of Gasoline. — The specific

gravity of gasoline, being less than that of water, is determined
by means of hydrometers made for liquids lighter than water.
A Baum6 hydrometer for testing liquids lighter than water is
showTi in Fig. 1. It consists of a glass tube, near the bottom
of which are two bulbs. The lower and smaller bulb is
loaded with mercury or shot, so as to cause the instrument
to remain in a vertical position when placed in the liquid
in the vessel a. The upper bulb b is filled with air, and its
volume is such that the whole instrument is lighter than an
equal volume of water.

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8 AUTOMOBILE CARBURETERS § 5

The point to which the hydrometer sinks when placed in
water is usually marked, the tube being graduated above and
below in such a manner that the specific gravity of the liquid
can be read directly. When placed in the liquid, the hydrom-
eter sinks so that the entire bulb, as well as a portion of
the neck, or stem, is beneath the surface.

The stem is graduated in much the same manner as a
thermometer. The reading on the neck at the point where it
emerges from the surface of the liquid indicates the degrees,
as they are called, or the heaviness, of the liquid. The
farther the hydrometer sinks into the liquid, the higher is
the numerical reading on the scale. The instrument, of course,
will sink farther into a light liquid than into a heavy one.

15« If a Baum6 hydrometer sinks to the 66° mark, the
liquid in which it is immersed has a density, or heavi-
ness, that is about .71 that of pure water. In other words,
as indicated by Table I, .71 is the specific gravity of
the gasoline. This means that a pint of the gasoline
is about .71 times as heavy as a pint of water. If the
hydrometer does not sink this far in the gasoline, it
is because the latter is heavier than .71 times the heaviness
of water and therefore has a higher specific gravity.

The reading on the scale of the Baumd hydrometer for the
heavier liquid has a lower numerical value than for the lighter
liquid. The specific gravity, on the other hand, has a higher
numerical value for the heavier liquid. It is therefore evi-
dent that by increasing the heaviness of a liquid its hydrom-
eter reading is decreased, and this corresponds to an
increased specific gravity.

Gasoline, like any other liquid, is heavier when it is cold
than when it is warm. Therefore, a gasoline that gives a
reading of 76° on the hydrometer on a summer day, when the
thermometer indicates a temperature of say 80°, will give
a lower reading on a winter day when the gasoline is as cold
as the freezing point of water.

16. Kerosene. — Owing to the greater ease with which
it may be vaporized, gasoline is practically the only fuel

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§ 5 AUTOMOBILE CARBURETERS 9

used in automobile engines. The use of kerosene is con-
fined ^most exclusively to internal-combustion engines of
the stationary type.

So far as their heating value per poimd is concerned, there
is not much choice between kerosene and gasoline, each
developing about 19,800 British thermal units per pound.
Kerosene, however, is about 10 per cent, heavier, so that a gal-
lon of kerosene has greater fuel value than a gallon of gasoline.

Ordinary kerosene varies in specific gravity (at 59° F.)
from .76 to .82. Exceptionally light kerosene, such as the
Pennsylvania light oil, has a specific gravity below .76.
The boiling point of kerosene of .76 specific gravity is 302° F.
and of kerosene of .82 specific gravity, 536° F. Kerosene
begins to give off vapor at from 100° to 12Q° F. Kerosene
is generally rated by its flashing point. This point is the
number of degrees of temperature to which it must be heated
before the vapors given off from the surface of the oil will
take fire from a flame held over the containing vessel. Thus,
oil of 15(P test is oil that will flash or take fire when heated
to a temperature of 150° F. Kerosene, at ordinary temper-
atures, should extinguish a lighted taper when the taper is
plunged into it.

17. Alcohol as a Fuel. — In the past alcohol has not

been used in the United States as an automobile-engine fuel
on account of the high internal-revenue tax imposed on it.
This tax having been removed, its use will no doubt become
quite common. In other countries, particularly in Germany,
it has become an important engine fuel, and is used also for
heating and, with incandescent mantles, for lighting. For
such use, it is denatured, or rendered unfit for drinking, by
the addition of poisonous ingredients, such as wood alcohol,
some other hydrocarbon distilled from petroleum, and some-
times coloring matter.

In tropical regions, notably in Cuba and in Central America,
alcohol can be produced so cheaply as to make it a strong
competitor of gasoline, which has the disadvantage of evapora-
ting much more rapidly than alcohol when exposed.

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10 AUTOMOBILE CARBURETERS § 5

18. There are two kinds of alcohol: methyl, or wood,
alcohol, and ethyl, or grain, alcohol. The former has been
found objectionable for use in internal-combustion engines,
because it apparently liberates acetic acid, which corrodes
the cylinders and valves.

19. Grain, or ethyl, alcoliol has a specific gravity of
.795, and may be obtained by distillation from com, wheat,
and other grains, potatoes, molasses, or anything containing
sugar or starch. When pure, it absorbs water rapidly from
the air, more rapidly in fact than it loses its own substance
by evaporation ; but when diluted to the proportion of about
85 per cent, alcohol and 15 per cent, water, it evaporates
practically as if it. were a single liquid and not a mixture.
In France, it is denatured for use in automobile engines by
the addition of 10 liters of 90° wood alcohol and 500 grams
of heavy benzine to ,100 liters of 90° ethyl alcohol. This
mixture costs, in France, about 38 cents a gallon, and to
reduce the rather high cost it is generally mixed with an
equal volume of benzol, which is a by-product of the coking
of coal and contains about 85 per cent, of benzine. In
Germany, benzol is added to the extent of 15 per cent, for
denaturing, no wood alcohol being used. The price of this
fuel is from 15 to 17 J cents a gallon.

20. As compared with gasoline as a fuel for internal-com-
bustion engines, alcohol exhibits several striking peculiarities.

First, the combustion is much more likely to be complete.
A mixture of 90° alcohol vapor and air will bum completely
when the proportion varies from 1 of the vapor with 10 of air
to 1 of the vapor with 25 of air, thus exhibiting a much wider
range of proportions for combustibility than is the case with
gasoline. As the combustion is complete, the exhaust is
practically odorless, consisting only of water vapor and
carbon dioxide.

Second, the inflammability of an alcohol mixture is much
lower. This is due partly, no doubt, to the presence of water,
which is vaporized with the alcohol in the engine and must
be converted into steam at the expense of the combustion.

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§5 AUTOMOBILE CARBURETERS 11

For these reasons, the compression of an alcohol mixture
is carried far above that permissible with a gasoline mixture,
without danger of spontaneous ignition. The rapidity of
combustion of alcohol in an engine is considerably less than
that of a gasoline mixture, and for this reason the speed of
alcohol engines must be somewhat slow.

21. With engines of equal size, practically the same
horsepower can be obtained when adapted to burning alcohol
as when adapted to burning gasoline. This is true in spite
of the fact that a pound of alcohol contains considerably less
heat energy than a pound of gasoline, and it is explained by
the fact that a pound of alcohol requires much less air for
its complete combustion than a pound of gasoline. In other
words, a larger quantity of alcohol than of gasoline is required
to make a cubic foot of explosive mixture. Approximately
speaking, if there is no surplus air in either case, 1 pound of
gasoline will make 210 cubic feet of explosive mixture, and
1 pound of alcohol will make 120 cubic feet. As a matter of
fact, a certain percentage of additional air is required, both
for the most rapid combustion and for the necessary economy
of fuel. So far as can be judged, a somewhat greater propor-
tion of air is advantageous with alcohol; but it seems to be
clear that from 50 to 60 per cent, more alcohol than gasoline
by weight is required to obtain the same power. On the other
hand, alcohol is about 25 per cent, heavier than gasoline, so
that 1 pound of gasoline has IJ times the volume of 1 pound
of alcohol. Consequently, if the weight of alcohol needed
for a given amount of work were 50 per cent, greater than
the weight of gasoline, the volume of alcohol required would
be only one-fifth greater, or in the proportion of 1.5 to 1.25.

22. Yaporlzatlon of Liiquld Fuels. — Liquids never
bum as liquids. To produce combustion, they must first
be vaporized and their vapors mixed with air in suitable
proportions. This process requires the addition of heat,
which may be secured by absorption or by radiation from
surroundings objects, and which will come mainly from the
combustion itself after that has been started. Liquids that

222—5

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12 AUTOMOBILE CARBURETERS g 5

volatilize at ordinary temperatures are highly dangerous if
their vapors are inflammable, and should be handled with
extreme care. If, like kerosene and the heavier oils, they do
not volatilize at ordinary temperatures, they are not so
dangerous. Both alcohol and gasoline give off inflammable
vapors at ordinary temperatures.

In automobile practice, the liquid fuel is vaporizod before
it enters the space where it is burned. The vaporization is
accomplished by bringing the liquid into intimate contact
with air. When the air and fuel vapor are thus mixed together
in proper proportions, the mixture can be ignited and burned
by the application of a lighted match, an electric spark, or
any sufficiently hot substance, as a piece of metal.

23. The vapor of any of the three liquids, gasoline,
naphtha, and alcohol, can be considered to be a gas so far
as its use in the engine is concerned. In fact, illuminating
gas is frequently made by mixing the vapor of gasoline or
naphtha with air, the proportion of the vapor being so great
that the mixture will not bum imtil more air is added to it.
This gasoline gas or naphtha gas is carried through pipes and
burned in the same manner as ordinary illuminating gas
made from coal. Kerosene does not vaporize so readily as
the other three liquids mentioned, the application of heat
being necessary to convert it into vapor and keep it in that
state. Alcohol vaporizes less readily than gasoline, but far
more readily than kerosene.

MIXTURES OF GASOLINE AND AIR

24. In considering the following discussion, it will be
well to bear in mind that gasoline is a name commercially
applied to a rather wide range of combustible liquids, some
of which are more accurately specified as naphtha, benzine,
etc. The portions of air and gasoline of any definite quality
must be kept within a limited range in order to obtain the
best results in the engine.

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§ 5 AUTOMOBILE CARBURETERS 13

A given volume of air, as a cubic inch, can absorb only a
certain amount of gasoline vapor, just as water can dissolve
no more than a certain amount of salt. A mixture containing
less than this amount of vapor is neither a saturated nor a
perfectly proportioned mixture; the less vapor it possesses,
the leaner it is said to be. A mixture containing more than
this amount of vapor is not a perfectly proportioned mixture
either; the more vapor it has, the richer it is said to be. The
proper mixture of gasoline and air for explosive purposes in
a gasoline-engine cylinder bums, at atmospheric pressure,
with a blue flame, and leaves little or no sooty, or carbon,
deposit on the walls of the vessel in which it may be burned.
Lean mixtures behave in the same way, except that when
they bum in a confined space, the pressure produced is less
than that produced by a perfect mixture, because the volume
of combustible mixture is less. The surplus air does not
bum; it is heated, however, and, of course, expands some.
A more intense explosion will be produced by a proper
amount of gasoline vapor and air if the two are first thoroughly
mixed together.

25. If there is present in a mixture more gasoline vapor
than the air present can take up, and the mixture is ignited,
a certain amount of the vapor will be consumed, leaving the
surplus un consumed. Inrushing fresh air may mix with the
vapor thus left over, and another explosion may result if
there is a flame present or if the material it comes in contact
with is hot enough to ignite it. Such a rich mixture bums
under atmospheric pressure with a yellowish flame and leaves
a sooty, or carbon, deposit.

Under all requirements, whether of economy or of power,
an intimate and uniform mixture is essential, and this should
take place before the charge is fired. This means early and
rapid evaporation, particularly at high engine speeds, and a
certain amount of heat. United States government tests
indicate that below an extemal temperature of about 60°
there is an advantage in supplying artificial heat to counteract
the cooling effect of the evaporative process. Heat should

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14 AUTOMOBILE CARBURETERS § 5

not be supplied in excess of the reqiiirements of the evapora-
tive process, however, as this tends to reduce both the density
of the charge and the maximum power of the engine.

26. As gasoline vapor is heavier than air, it tends to
sink to the bottom of a vessel containing it, and unless
agitated it mixes but slowly with the air above it. For this
reason, a room in which gasoline vapor is present cannot be
well ventilated by openings near the ceiling; but openings
through the floor or under a door will allow the vapor to pass
out. The room can also be ventilated by a flue whose
bottom opening is at the floor, provided there is a current of
air passing upwards through the flue. If the flue has no draft,
as may be the case in damp weather, some artificial means,
such as a fan or a coil of steam pipe, must be used to induce it.

27. Proportions of Gasoline and Air. — Economy
requires that, at the time of ignition, each particle of fuel
shall be in contact with its proportion, or more than its
proportion, of air. On the other hand, maximum power in
an engine of definite size is obtained by burning the greatest
practicable amount of fuel, and, consequently, by supplying
fuel somewhat in excess of the chemical combining proportion,
in order to utilize the limited cylinder capacity to its fullest
extent. This agrees with the experience of practical motor-
ists, who know that an excess of gasoline is required for easy
starting, a rather rich mixture for extreme power, and a
weak;^ r mixture for economy. An excess of fuel is, to an
extent, a corrective for imperfect mixing and gasif)dng of
the charge.

The theoretical combining proportions of gasoline and air
are about 1 part of gasoline to 15.4 parts of air, by weight,
or about 5 ounces of gasoline to 100 cubic feet of air. By
volume, at sea level, this is approximately 1 part of gasoline
to 8,500 parts of air. For maximum power, the proportion
should be 1 to 6,500, and for the most economical restilts
the proportion should be 1 to 10,000 or 12,000, which
is well within the ignitible limits, provided the charge is
properly mixed and gasified.

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5 5 AUTOMOBILE CARBURETERS 15

GASOIilNE 8UPPI.Y TANKS

28. Classification. — The tank that carries the supply
of liqtiid fuel for an automobile may be located either at a
level considerably higher than the carbureter, so that the
liquid will flow freely, or at a level lower than the carbureter,
so that there will be no gravity flow to the latter even when
the tank is ftill. When the tank is placed lower than the
carbureter, either air or gas pressure is used to force the
liquid out of the tank and into the carbureter. A tank so
located is called a compression tank or compression-feed tank.
If the tank is located above the carbureter, it is called either
a gravity tank or a gravity-feed tank,

29. Compression Gasoline Tanks. — In some com-
pression tanks, after the tank has been filled with fuel,
air is pumped in by hand until the pressure is sufficiently
high. After the engine begins to run, the pressure of its
exhaust is generally utilized to maintain the pressure in the
compression tank. This is done by connecting a pipe from
the engine, at a point just outside the exhaust valve of one
cylinder, to the top of the fuel tank. The hand pump is
ordinarily connected to this pipe line or interposed in it.
In any case, there must be a check-valve in the pipe line
in order to prevent back flow from the tank when the pres-
sure falls at the engine. A wire-gauze screen also is generally
placed in the pipe, so as to prevent particles of soot or carbon
from being blown through the pipe into the tank.

At first, it might seem that connecting the engine and tank
in this manner is dangerous, on account of the possibility of
a spark or flame being blown into the tank. However, the
pipe is generally so small that a flame cannot pass through
it, and, owing to the cooling effect of the walls, a spark would
in all probability be cooled below the igniting temperature
before reaching the tank. But even if a flame or a spark
were blown into the tank, there would in all probability be no
ignition and consequent explosion, because the air in the
tank is ordinarily so saturated with the vapor of volatile

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16 AUTOMOBILE CARBURETERS § 5

fuel that it cannot be ignited by any means. A possible
exception to this, however, might occur when a large quantity
of air has been pumped into a partly empty tank immediately
before the engine is started.

30. Auxiliary Compression-Feed Gasoline Tank.

In some compression-feed systems, the necessity of pumping
air into the compression fuel tank is obviated by the use of
a small auxlllai*y fuel tank that is placed at a level
higher than that of the carbureter. The compression in the
main fuel tank forces the liquid up into the auxiliary tank,
from which it flows to the carbureter. The auxiliary tank
is thus always kept full, or nearly full, while the engine is
running, so that when the engine stops there is plenty of
fuel in the auxiliary tank. This fuel remains in the auxiliary
tank even if the pressure in the main tank falls, as when the
latter is opened for filling. All the fuel in the auxiliary tank
will flow by gravity, if necessary, to the carbureter to keep
the engine running. There is, therefore, always enough fuel
in the auxiliary tank to start the engine and keep it running
until the pressure in the main tank has become great enough
to force the liquid into the auxiliary tank and carbureter.
This auxiliary tank is generally placed on the dash of the car,
where it can be readil}'' seen by the driver. When this tank
is so located and has a large capacity, it not only serves to
indicate the exhaustion of the supply of fuel in the main
tank, but furnishes enough fuel to run the car some distance
after giving such an indication.

31. Gravity Gasoline Tanks. — The grravlty system

of feeding gasoline to the carbureter requires very little
attention and no maintenance of air pressure by means of a
hand pump or other device; also, the engine may be started
without any reference to the length of time that may have
intervened since it was last stopped. There must always be
at least a small opening in the upper portion of a gravity
tank, so that air can pass into the tank as the fuel flows out;
otherwise, a partial vacuum will be formed in the tank and
the flow of fuel will gradually decrease until the carbureter

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J 5 AUTOMOBILE CARBURETERS 17

does not receive enough to keep the engine running. The
smaller the air space in the upper part of the tank, the shorter
is the time required for this to occur. Only a minute hole is
needed to allow the air to pass in. It is seldom advisable,
however, to make the hole smaller than ^ inch in diameter.
If made smaller, it is liable to become clogged, which condi-
tion is the same, so far as the outflow of gasoline is concerned,
as if there were no vent in the tank.

32. A tank may be placed high enough above the car-
bureter for satisfactory operation on level roads and slight
grades, but when located in the rear of the carbureter, the
tank may be too low for good operation when ascending very
steep grades. Under such conditions, a small particle that
would cause no trouble on level roads or slight grades may
clog the spray nozzle or inlet valve and starve the engine just
when hard work is required of it. One way to remedy such
a trouble is to shut off the gasoline at the tank and then
disconnect the supply pipe from the carbureter and in its
place insert a rubber tube attached to the tire pump. Air
should then be pumped through the pipe until the particle
is dislodged. The farther back the gravity tank is placed
from the engine, the greater will be the change in level of the
gasoline in the carbureter and tank for a given increase in the
grade.

33. Reserve Gasoline Supply Tank. — A reserve
compartment is provided in several makes of gasoline
tanks. This compartment has a capacity of a gall9n or more,
and is so arranged that the gasoline will not flow out until
a valve, which is ordinarily kept closed, is opened. Thus,
after all the gasoline is used from the main part of the tank,
there is still a reserve of a definite quantity, which is generally
sufficient to carry the car to some source of supply. It is
advisable to have this reserve tank so located that, when
putting in a fresh supply of fuel, it will first enter the reserve
tank and then overflow into the main compartment. In
this way the gasoline in reserve is always fresh.

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34. Methods of Measuring Quantity of Gasoline In
Tanks. — A gasoline tank deptli i^uge, or Indicator,

for showing the depth of gasoline in the supply tank is
illustrated in Fig. 2. A float a rests on the top of the gaso-
line and rises and falls with it. A slot in the center of the
float engages with a twisted flat stem b. As the float rises,
this stem is moved aroimd and carries with it a hand, or

pointer, c, which moves
over a dial graduated to
indicate the quantity of
gasoline in the tank.
Rotary motion of the float
a is prevented by the frame
d, with which lugs at the
edge of the float engage.

35. A simple way to
determine the depth of
gasoline in a tank is to
insert a straight stick or
wire through the filling
hole until the end touches
the bottom of the tank
and then quickly withdraw
it and note how far from
the bottom it is wetted by
the gasoline. A graduated
rule made especially for this
purpose is very convenient.
Many rectangular tanks are
of such dimensions that a depth of 1 inch means 1 gallon of
liquid; hence, the tank contains as many gallons of gasoline as
there are inches from the bottom to the surface of the liquid.
By commencing with an empty tank and pouring in a half
gallon or a gallon of gasoline at a time and then marking the
height each measureful produces in the tank on a clean stick,
a very convenient and accurate gauge can be readily made.
Anything used for this purpose should, of course, be clean.

Fig. 2

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§ 5 AUTOMOBILE CARBURETERS 19

TYPES OF AUTOMOBILE CARBURETERS

pbincipIjES of operation

CLASSIFICATION ANB GENERAL REQUIREMENTS

36. Definition. — A carbureter is an appliance
for vaporizing liquid hydrocarbons by passing air either
over the surface of or through the mass of the Uquid, or
by atomizing the liquid and mixing it with air. The air
thus becomes saturated with the vapors of the hydrocarbon.
This mixture invariably contains too large a proportion of
vapor for an explosive mixture ; therefore, before the mixture
can be exploded in the engine cylinder, it requires the further
addition of air.

37. Classification. — Carbureters may be divided
into three classes, as follows:

1. Those which use a large surface of the hydrocarbon,
generally spread out in thin layers, and over which air is
compelled to pass. These, for the sake of convenience, will
be called surface carbureters.

2. Those in which the liquid fuel is placed in any con-
venient reservoir, usually of great depth in proportion to
the horizontal dimensions, and the air is compelled to pass
through the body of the liquid. These may be called fil-
tering carbureters.

3. Those which vaporize, or atomize, the hydrocarbon and
inject it into a current of air. These are called spray car-
bureters. ^

The first two types preceded the third in point of time,
but the spray carbureters are now used almost exclusively.

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20 AUTOMOBILE CARBURETERS § 5

38. Requirements for an Automobile Carbureter.

A successful automobile carbureter must fulfil the following
requirements:

1 . It must give a practically uniform mixture, whether the
demand on it is light or heavy, within the range of the speed
actually attained by the engine. The mixture must be the
same when the engine is running slowly with the throttle
wide open, as when going up a hill, or slowly with the throttle
nearly closed, as when coasting or traveling slowly on the
level, or when nmning at top speed with the throttle wide
open.

2. It must not freeze up in cold weather because of con-
densation of moisture from the air and freezing in the mixing
chamber.

3. It must not be unduly sensitive to changes in the
quality of the gasoline, and it must admit of easy adjustment
for such ordinary variations in density as are likely to be
encountered.

4. It must not be unduly sensitive to changes in the level
of the car, as when climbing or descending a hill, or when
turning off the road into the gutter.

5. It must vaporize the gasoline reasonably well when
starting in cold weather.

G. It must operate equally well whether the engine has one
or two cylinders giving intermittent suction, or a larger
number of cylinders giving practically a continuous suction.

7. The quality of the mixture delivered must not be
affected by the vibration of the car.

8. The carbureter must not be exposed more than neces-
sary to the entrance of dirt, and all parts to which dirt is
likely to find its way must be readily accessible for cleaning.

It is evident that with so many requirements there is
no carbureter made that fulfils all of them equally well.

39. Objections to Surface and Filtering Carbu-
reters. — Ir\ the early days of the internal-combustion engine,
the fuel was vaporized simply by having the air drawn over
it, or in some cases drawn through it in the form of bubbles

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§ 5 AUTOMOBILE CARBURETERS 21

by the suction of the piston. Sometimes, to give an increased
surface for evaporation, a spiral coil of flannel or other suitable
material, as wicking, was arranged so that it would stand
partly out of the gasoline, and the air would be drawn over
the surface of the gasoline and the wicking. All devices of
this sort have gone out of general use, on account of several
important objections: Plain surface evaporation requires a
very large surface in order to evaporate the gasoline fast
enough to supply an engine l^rge enough for average
demands for power. Again, gasoline is not a homogeneous
compound; it is a mixture of light and heavy products of
petroleum. When it is evaporated from the surface, the
lighter constituents are evaporated first, and hence in time
the carbureter contains only the denser portion or stale
gasoline i as it is called, which will not evaporate with suf-
ficient rapidity to supply the air with the amount of hydro-
carbon necessary for explosion. Another objection to car-
bureters of this sort is that the rate of evaporation of
gasoline will depend very largely on its temperature, and it
is difficult to supply the heat necessary to maintain the
required temperature. The gasoline is cooled by its own
evaporation, and the heat to make up for this must be sup-
plied in some way, usually by warming the air before it
goes into the carbureter by drawing it thrdugh a jacket
around the exhaust pipe of the engine. Sometimes the
gasoline is warmed by means of a jacket around the car-
bureter, through which is circulated water from the jacket
of the engine. If the engine speed is at all variable, the
supply of heat will vary. It follows that the gasoline, or
the air that evaporates it, receives more heat at some times
than at others, and the richness of the mixture fluctuates
accordingly.

40. Advantapre of Spray Carbureters. — For the rea-
sons just stated, the surface and the filtering carbureters
for internal-combustion engines have been abandoned, their
place being taken by a large variety of forms of spraying
devices. In these, the gasoline is given to the air in the

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§5

form of a jet, or spray, that is drawn from the supply by
the air-current. When the air is sufficiently warm, this
spray is evaporated and a fairly constant mixture of air and
gasoline vapor is thus obtained.

PRINCIPLES OF SPRAY CARBURETERS

41, The spray carbureter has a nozzle with one or more
small, almost minute, openings, or orifices. For convenience
of discussion, it will be assumed at first that the nozzle has
only one orifice. The air passing to the engine draws the
gasoline out of the orifice of the nozzle. When the gasoline
thus drawn out forms a spray, as is usually the case, it
almost instantly vaporizes and mixes with the air, so as to
form, under favorable conditions, a combustible mixture.

^^^^

Fio. 3

Fig. 4

In some carbureters, the spray orifice is slightly above the
constantly maintained level of the body of gasoline to which
it connects; in others, the orifice is below the level of the
gasoline, and it is automatically stopped by a valve so that
' the liquid cannot flow from it when not required for enriching
the air.

Some of the elements of a spray carbureter are shown in
Fig. 3. At a is shown the gasoline reservoir, and at 6, the

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§ 5 AUTOMOBILE CARBURETERS 23

nozzle, which has an orifice that opens vertically upwards
and is connected to the gasoline in the reservoir a by the
passage shown. This passage is considerably larger in sec-
tional area than the orifice. The nozzle is surrounded by a
vertical tube c, which is closed at the top and is connected
at the bottom with a cylinder d, into which fits a free-moving
piston e. This elementary device can be used to illustrate
partly the principle of operation of a carbureter.

In order to illustrate the principle of operation, it will be
assumed that the top of the nozzle b is at the same height,
or on the same level, as the surface of the gasoline in a.
If the piston e is moved downwards, as indicated by the
arrow on it, a partial vacuum will be created in the space
surrounding the nozzle and a spray, or jet, of gasoline will be
drawn out of the nozzle by suction, because the pressure
against the liquid at the orifice is lower than the atmospheric
pressure on the surface of the liquid in the reservoir a.

42, The apparatus shown in Fig. 4 differs from that just
described in that the tube c is open at the top and is shorter,
so as not to extend far above the nozzle b. This tube is also
somewhat contracted at the top, so as to make the opening
leading to the atmosphere smaller than that through the
body of the tube. If the piston e is moved upwards, so as
to force air out through the tube c past the nozzle J, as
indicated by the feathered arrows, a spray of gasoline will
be drawn out of the nozzle. In this case, the pressure of the
air passing out by the nozzle is greater than that of the
atmosphere acting on the surface of the liquid at a. Under
this condition, no gasoline would be drawn from the nozzle
if it were not for the effect of the velocity of the air-current.
The moving air-current has a tendency to form a partial
vacuum immediately around the nozzle opening. It is by
this action of the moving air that the gasoline is drawn out.

43. In Fig. 5 it may be assumed that the same reservoir
and nozzle are used as . in the preceding cases. The tube c,
however, is open at the bottom, and the cylinder d and
piston e are connected to its upper end. If the piston is

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moved upwards, as indicated by the arrow on it, a current
of air will be drawn into the bottom of the tube and up
through it into the cylinder d, as indicated by the feathered
arrows in the tube c. The air pressure in the tube c must be
lower than that of the atmosphere in order to cause this
flow of air into and through it. In this case, a spray of gaso-
line is drawn out by the suction and the velocity of the air-
current. If the air flows through the pipe c at a velocity as
high as is common in automobile practice, the gasoline will
be drawn from the reservoir until its level falls as much as

Pro. 5

1 inch, or, in some cases, 2 inches below the top of the
nozzle.

44, In Fig. 6, the reservoir and nozzle are the same as
before, but the tube c is open at the top and the cylinder d
and piston e are located at the lower end of the tube. If
the piston is moved downwards, as indicated by the arrow
on it, no gasoline will be drawn from the nozzle 6, although
the air pressure in the tube c at the level of the nozzle must
be lower than that on the surface of the liquid in a in order
to draw air into the tube. This lower pressure at 6, if acting
alone, would, of course, draw gasoline out of the orifice.
But this is prevented by the action of the air-current, which,
striking against the orifice, more than counteracts the suction

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AUTOMOBILE CARBURETERS

tendency to draw out the gasoline. If the tube c were
extended upwards to a considerable distance, or to a short
distance and reduced in the area of its opening, as in Fig. 7,

^^^^^

Fig. 6

Pig. 7

then the suction caused by the downward movement of the
piston e would be greater than the opposing effect due to
the velocity with which the air strikes the nozzle 6, and
gasoline would be drawn from the nozzle.

45, Elementary forms of carbureting devices in which
the air pipe is horizontal are illustrated in Figs. 8, 9, and 10.

Fig. 8

^^_^.,,.,.„.,.,.^^

^"^

3E2

In Fig. 8, the gasoline reservoir is connected by a passage
to the nozzle 6, whose orifice opens toward the left. The
horizontal air pipe c extends only slightly to the left beyond

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§5

the orifice 6, and is somewhat contracted in diameter at the
end. The right-hand end of the air pipe c is connected to a
cyUnder d, into which is fitted a piston e. The bottom of

Pig. 9

the orifice b is at the same level as the surface of the gasoline
in the reservoir a. By moving the piston e toward the left,
as indicated by the arrow on it, the current of air thus caused
to flow out past the nozzle 6, as indicated by the feathered
arrows in pipe c, will draw a spray of gasoline from the orifice.
In this case, the drawing of the gasoline from the nozzle is
due to the velocity of the air-current, because the average
pressure of the air-current as it passes b must be greater than
that of the atmosphere acting on the liquid in the reservoir a ;
otherwise, the air would not flow out of the tube into the
atmosphere.

Pig. 10

46. In Fig. 9, the nozzle b has its orifice opening toward
the end of the tube c that is connected to the piston. If
the piston e is moved toward the right, as indicated by the

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§ 5 AUTOMOBILE CARBURETERS 27

arrow on it, air will be drawn through the tube c, as indicated
by the feathered arrows. The gasoline will be drawn from
the orifice by the combined action of suction and velocity.

47. In Fig. 10, the orifice is at the top of the nozzle b
and opens vertically upwards. If the piston e is moved
toward the right so as to draw in air through the tube c,
gasoline will be drawn from the nozzle by both the suction
and the velocity of the moving current of air. This case is
far less simple than others that have been discussed, for the
reason that the shape of the top of the nozzle has a very
marked effect on the action that the velocity of the air-
current produces, either to draw gasoline from the nozzle or
to force it back into the nozzle. If the top of the nozzle is
made flat and horizontal, and the orifice is located at the
center, the air velocity will tend to draw the liqtiid out.
If the top is made flat, or, more correctly, a plane surface,
and is inclined so that its lowest side is next to the piston,
the velocity of the air-current flowing toward the piston
will have a greater effect toward drawing out the gasoline
than when the top is flat and horizontal. This condition
approaches, in a measure, that illustrated in Fig. 9. On
the other hand, if the top is a plane surface, and is inclined so
that its lowest edge is next to the intake end of the pipe
through which the air is drawn, the velocity will have less
tendency to draw out the liquid than when the surface is
flat and horizontal ; and if the inclination is great, the velocity
effect will be to press against the gasoline and force it back
into the orifice rather than to draw it out. This latter
condition approaches one in which the nozzle opens horizon-
tally toward the air inlet through which the air is d^awn in
by suction.

48, The following is a brief summary of the preceding
discussion: A current of air or of gas flowing past an open
nozzle in the direction toward which the orifice of the nozzle
opens tends to draw liquid from the nozzle when the orifice
is filled with the liquid; but when the direction of air or gas
flow is toward the orifice, the tendency is to force the liquid

222—©

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28 AUTOMOBILE CARBURETERS § 5

back into the orifice. Reduction of pressure at the orifice
tends to draw liquid from the orifice by suction.

By varying the form of the nozzle about the orifice, effects
similar to those produced by inclining the surface of the
nozzle in a horizontal air tube, as mentioned in connection
with Fig. 10, can be obtained to a marked degree. Such
variations do not appear very frequently in commercial
carbureters. It is not unusual, however, to find the air tube
contracted in diameter just opposite the gasoline orifice.
This contraction is not made suddenly, but the variation of
diametfer from the larger to the smaller size is gradual.

CARBURETER CONSTRUCTION

FLOAT-FEED SPRAT CARBURETBttS

49. The almost universally adopted method of maintain-
ing a constant, or nearly constant, level of gasoline in the
reservoir of the carbureter, is by means of a float to which
is attached a valve that cuts off the inflow of gasoline from
the supply tank when the liquid rises to a predetermined level.
The float is, of course, placed in the gasoline contained in
the carbureter reservoir. This device is called a float feed.
The float is adjusted to maintain a gasoline level slightly
lower than the top of the nozzle. This is done in order to
secure a margin of safety to allow for inaccurate operation
of the float and valve, so that there will not be excessive
flow of gasoline from the nozzle in case the float allows the
liquid to rise slightly above its normal level ; also, to prevent
dripping when the car is idle, and overflow due to the tipping
of the carbureter when the car is out of level, as on a hill or
the side of a crowned roadway, or on account of vibration.

The average height of the spray nozzle above the normal
gasoline level when the carbureter is level, as found in general
automobile practice, is about ^ inch. This distance varies
according to the design of the carbureter. It is sometimes,
although not often, less than ^ inch, and it is seldom

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AUTOMOBILE CARBURETERS

more than | inch, although it may be as much as A inch or
more in some carbureters.

50, A simple form of float-feed carbureter is

shown in Fig. 11. Gasoline from the supply tank enters
the bottom of the carbureter at a and flows up past the
valve b into the float chamber c, which is not perfectly air-
tight above the float. Part of the gasoline flows into the pas-
sage leading to the spray nozzle d. As the gasoline rises in the
float chamber it lifts the float e and also the valve b attached
to the float. When the gasoline reaches a level slightly below

the top of the spray nozzle J, the valve b closes the inlet
passage to the float chamber and thus stops the inflow of
gasoline. The upper end of the chamber h is connected to
the engine intake. The suction of the engine draws in air
at the opening / of the air passage g, past the nozzle d, with
considerable velocity, into the mixing chamber h and out at
the top thereof, as indicated by the arrows. On account
of the velocity of the air passing the nozzle d, and the pressure
at d, which is lower than that upon the surface of the gasoline
in the float chamber c, gasoline is dra^Ti out from the spray
nozzle ; the float e therefore descends slightly by the lowering

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30 AUTOMOBILE CARBURETERS § 5

of the gasoline in the float chamber, and the float valve b
is slightly opened, so as to allow more gasoline to enter and
thus maintain a nearly constant level in the float chamber.
The vaporization of the gasoline requires heat, part of
which is drawn from the walls of the air passage or mixing
chamber h. This withdrawal of heat leaves the metal around
the air passage cold, even at times below the freezing point
of water. The coldness retards the rapidity of vaporization,
and in some cases interferes with the satisfactory oper-
ation of the carbureter. In order to obviate this, a jacket
space i is provided around the mixing chamber, and exhaust
gas from the engine or water from the cylinder water
jackets may be circulated through this jacket space to
keep the carbureter warm.

51. When cranking an engine by hand to start it, the
suction and velocity of air through the carbureter are generally
not great enough to draw sufficient gasoline from the spray
nozzle of a float-feed carbureter to make a mixture rich
enough to be ignited in the engine. This is principally because
the normal level of the gasoline is below the top of the spray
orifice, as has been stated. Some hand-operated device by
means of which a small quantity of gasoline can be caused
to flow into the air passage is therefore generally incorporated
in carbureters of the float-feed type. This gasoline is then
readily vaporized, and the vapor is mixed with the air drawn
into the carbureter, so that the engine receives a combustible
mixture while being rotated at rlow speed by hand. The
flowing of gasoline into the air passage of a carbureter by
hand-operated means, as just described, is called priming the
carbureter.

The carbureter. Fig. 11, can be primed by pressing down
with one's finger on the top of the stem extending from the
float through the cover of the float chamber. When the valve
and float are thus depressed, gasoline will flow in from the
supply tank, past the float valve, and out of the spray nozzle.
Other methods of priming -the carbureter are described
in connection with the carbureters on which they are used.

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AUTOMOBILE CARBURETERS

COMPENSATING CARBURETERS

52. The carbureter shown in Fig. 1 1 may give a mixture
richer in gasoline when the air passes through it rapidly
than when it passes at a slower rate. In order to produce
a mixture as nearly constant as possible in its proportions
of air and gasoline vapor, an automatic air valve is very often
placed on the carbureter to control the inflow of air into the
carbureter. Such a carbureter is shown in Fig. 12. It is
a modification of the one already described. The gasoline
from the supply tank flows in at a and passes into the float

Fig. 12

chamber until the float c rises so as to close the float valve d
when the level of the gasoline nearly reaches the top of the
spray nozzle e. A comparatively small air intake, as shown
at 6, is always connected to the mixing chamber g by an
open passage. An auxiliary air intake is closed by the
compensating automatic air valve / when the suction produced
by the piston and hence the demand for mixture are light;
but when the engine is drawing mixture rapidly, the suction
is sufficient to draw the spring-closed, compensating air

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valve / open and automatically admit more air. This admis-
sion of air through the compensating valve restricts both the
suction and velocity effects at the spray nozzle e, and also

44f

X).- ;

Pio. 13

supplies pure air to dilute the overrich mixture formed in
the small air passage leading from the open intake h past the
spray nozzle into the mixing chamber.

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§ 5 AUTOMOBILE CARBURETERS 33

The two plugs h and i are provided for cleaning the carbu-
reter of any foreign matter, as dirt, and water that may be
carried in with the gasoline. As almost all such matter is
heavier than gasoline and tends to settle to the bottom, it is
only necessary to unscrew these plugs and cause a little
gasoline to flow through in order to clean the carbureter.
The annular jacket ; is connected, by pipes not shown, with
either the exhaust pipe or the water-jacket of the engine, and
this serves the purpose of supplying the heat required by the
gasoline in the process of evaporation, thus preventing
condensation and freezing of the moisture in the air.

To start the engine, the stem k is depressed, thus opening
the valve d and permitting the gasoline to escape freely
from the spray nozzle. In this way a sufficient quantity of
gasoline is allowed to gather in the intake pipe to produce,
simply by evaporation, the mixture necessary for starting.

53, The carbureter illustrated in Fig. 13 embodies
some of the features of the one shown in Fig. 12. The arrange-
ment of the parts relative to each other is different, however.
The chief differences are that, in Fig. 13, the float chamber
and float are concentric with the spray nozzle, and that the
float valve c is at one side of the float and is closed by a
weight attached to its stem. The downward pressure due
to a weight is less apt to change than that due to a spring.
When the float d rests on the float lever e, the gasoline enters
the carbureter at 5 and flows past the needle valve c into
the float chamber 6, which contains the circular float d.
The float lever e is pivoted tb the body of the carbureter by
a pin p. The weight of the float on the float lever lifts the
float valve c. The rising of the float as the gasoline flows
into the float chamber allows the valve to descend and close
the gasoline-inlet passage from the supply tank.

In a similar carbureter, a spiral spring, in addition to the
weight of the valve itself, is employed to close the valve c,
and the ends of the lever e, which are extended to the center
of the float chamber, are turned up so that the operation of
the lever is controlled by the part of the float very near the

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34 AUTOMOBILE CARBURETERS § 5

center. By this construction, the tipping of the carbureter
to the right or the left has less influence on the amount of
gasoline that the float and its valve will allow to flow into the
float chamber. By using a circular float around the spray
nozzle, the height of the gasoline in the nozzle is less affected
by the tipping of the carbureter than is usually the case
where the float is in a separate chamber from the spray
nozzle. Furthermore, as the arm of the lever connected
to the float is much longer than that acting against the
weight, it is possible to use a heavier weight than could other-
wise be employed, and a much more positive closing of the
valve is secured than if the float were to act directly on
the valve.

54. The mixture passes out of the carbureter to the
engine from the top of the carbureter, as indicated by the
arrows, Fig. 13. When the engine is taking only a small
amount of mixture, all the air enters the carbureter at the
bottom through the wire-gauze screen g, and flows up through a
and past the spray nozzle. The course of the air under this
condition is indicated by the full arrows. If the demand for
mixture becomes great, the increased suction will open the
automatic compensating air valve h against the resistance
of the spring i. Air then also enters the carbureter as indi-
cated by the broken arrows and mingles with the highly car-
bureted mixture coming from the passage at the spray nozzle.

The pressure of the air-valve spring i against the air valve
can be adjusted by means of the threaded bushing fe, against
which one end of the spring bears. The extent of the lift
of the air valve is limited by the adjustable screw /, the
stem of which passes loosely over the valve stem and forms
a guide in which the valve stem slides. The spray-nozzle
orifice is partly closed by a needle valve, the stem / of which
extends downwards to an external handle. A portion of
the stem / is threaded into a nut. The area of the spray-
nozzle inlet can be adjusted by turning the needle valve by
means of its external handle, and the flow of gasoline from
the supply orifice can thus be regulated.

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AUTOMOBILE CARBURETERS

A throttle valve t is located in the mixture passage near
the outlet of the carbureter. This valve is a thin disk of
sheet metal motmted on a spindle u that lies across the center
of the passage. A lever arm / for operating the throttle
valve is fastened to the external end of the valve stem.
A short arm w on the throttle lever strikes against the end of
a screw y when the throttle is nearly closed. This screw

Pig. 14

is adjustable and may be set so as to prevent the complete
closing of the throttle. This adjustment can be made so that
just enough mixture will pass the throttle to keep the engine
running idle when the car is at rest and the throttle closed as
completely as the adjusting screw will permit.

The gasoline level that the float maintains can be regulated
by screwing the adjustable weight along the threaded stem c

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36 AUTOMOBILE CARBURETERS § 5

of the float valve ; it is lowered by screwing the weight upwards
and is raised by screwing the weight downwards. To prime
the carbureter, the float valve is lifted by taking hold of the
projecting upper end m of the valve stem with the fingers.

55, The carbureter shown in Fig. 14 differs from those
previously described in a number of ways. The gasoline enters
at a, and if the float d is low enough, the valve e is held open
so that the gasoline will flow into the float chamber until
the float rises and the gasoline is shut off by the lowering of
the valve e. In the passage b is an automatic air-inlet
valve / that is closed by the spring g. This valve does not
entirely close the air passage when it rests on its seat, for
at the bottom is left an opening through which sufficient air
can enter for the engine at its lowest speed. As the suction
increases, this valve opens against the spring g, thereby
admitting a larger quantity of air. All air that enters
passes downwards, instead of upwards, as in most carbureters,
past the spray nozzle h and strikes against the end of the
nozzle. When the velocity of this down-flowing- air is
sufficient, as at high engine speed, it has a tendency to check
the flow of gasoline from the spray nozzle. The nozzle h
projects into the middle of the air passage, and the cork
float is made in the shape of a horseshoe in order to fit the
peculiar shape of the float chamber. As the opening of the
spray nozzle is exactly in the center of the float chamber,
the carbureter is not much affected when tilted. By means
of the pointed stem i, the opening in the spray nozzle can
be adjusted. The throttle valve / is opened and closed
by means of the lever k; the mixture of air and gasoline
passes through in the direction indicated by the arrow.
Adjustment of the automatic air valve / is obtained by
modifying the tension of the spring g. This is done by
screwing up or unscrewing the shouldered stem /, which
extends through the valve / to guide it, but is not attached to
it. A drain cock m is provided at the bottom of the float
chamber for the purpose of emptying or for drawing off
water that may have got into it.

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In starting the engine, the float d is depressed by means
of the lever n, which depresses the pin, or priming device, o.
This allows the level of the gasoline to rise above the nozzle h,
so that enough gasoline can enter the air passage to start
the engine.

-^m

Fio. 16

56. The same company that makes the carbureter shown
in Fig. 14 makes a slightly different model in which the
compensating valve, when closed, allows no air to enter
through the passage h ; but there is always open a passageway
for air from the bottom of the carbureter up around the

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38 AUTOMOBILE CARBURETERS § 5

spray nozzle into the main air passage, and the spray nozzle
is exactly even with the lower side of the main air passage.
Thus, all air from the fixed air opening for low engine speeds
is drawn upwards through a small opening past the spray
nozzle toward the engine connection c, and the extra air
for higher speeds is drawn downwards against the opening
in the spray nozzle.

A later model, made by the same concern, operates on
practically the same principle, although it is a little different
in shape, a shutter valve being placed in the auxiliary air
intake. This shutter valve may be closed to make the
starting of the engine easier in cold weather. When closed
or partly closed, it restricts the entrance of air and causes
greater velocity of the air from the fixed opening past the
spray nozzle, thereby producing a richer mixture.

57. Another type of compensating float-feed spray
carbureter is shown in Fig^ 15. The air enters at a and the
gasoline at h. The height of the gasoline is controlled by
the float c which, as it falls, presses on the levers d and raises
the weighted needle-valve stem e. When the float rises,
the needle valve is closed by its own weight. As the gasoline
comes from the float chamber, it issues from a number of
very sn^all slots / in the conical head of the spray plug g.
This plug is drilled upwards from the bottom, and then later-
ally, as shown by the dotted lines, to admit the gasoline to
the space beneath a conical cover, or hood, A. The division
of the entering gasoline into a number of very small jets
(from 10 to IG) insures a much more rapid mixing with
the air than when the spray enters in a single jet. The air
coming up from a strikes the hood h, which is pierced at
and near the top with a number of small holes through
which the air passes on its way to the throttle valve i and
thence to the engine. The hood h is attached to the stem /,
to the other end of which is connected a piston k working
against a spring in an air dashpot.

When tlie demand for mixture is small, the hood remains in
the position shown, and practically all the air flows up through

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40 AUTOMOBILE CARBURETERS § 5

the hood, past the spray plug, and out through the small
holes in the upper portion of the hood. As the demand for
mixture becomes great, the increased suction and velocity
lift the hood against the resistance of its spring, thus opening
an annular air passage around the outside of the bottom of
the hood. This allows part of the air to be diverted and to
flow outside of the hood, so as not to affect the gasoline spray.
The lifting of the hood opens up a freer passage for the
air from the bottom of the carbureter to the portion above
the spray nozzle. The effect of the lifting of the hood is to
limit the increased combined effect of the greater suction and
velocity, and therefore keep the mixture at least approxi*
mately constant in quality.

58. The purpose of the air dashpot connected to the
hood h is to check the pulsations of the latter when the
engine has only one or two cylinders. Although the hood is
made as light as possible, owing to its inertia it does not
follow perfectly the variations of the air-current when the
suction is not steady. The effect of the dashpot, however,
is to cause it to lift to an extent determined by about the
average intensity of the suction, and to remain in prac-
tically that position from one impulse to the next.

The carbureter is primed by unscrewing the valve / a
fraction of a turn and thus permitting the gasoline to escape
directly into the intake pipe a. A spring m insures the closing
of the valve when released. The throttle valve i is elliptic
in shape, as indicated, so that it will not have to be turned to
an angle of 90° from the wide-open to the closed position.
Connected to the exhaust pipe is a jacket n that serves to
supply the heat required for evaporation.

In another form of this carbureter, a stop-screw is provided
to limit the lift of the hood, and a needle valve, adjustable
from the bottom, is provided to restrict the rate of flow of
the gasoline to the spray plug.

59. Another carbureter with an automatic compensating
valve is shown in Fig. 16 (a) and (6), the two views being
taken at right angles to each other. The air enters through

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§5

AUTOMOBILE CARBURETERS

the slits o, view (a), in a shutter that can be rotated so as to
close them or give them the amount of opening desired. It
then flows through the openings b in the standpipe c, which
is made small in order to give the air considerable velocity as
it passes upwards past the spray nozzle d. The carbureted
mixture is then diluted by air coming through the automatic
valve e, and the final mixture passes out through the throttle

£f

Fio. 17

valve / into a pipe that bends upwards and leads to the
cylinders. The gasoline enters at g, view (6), and the float,
as it rises, causes the small levers h to push the needle-valve
stem i downwards, thus stopping the flow of gasoline. By
means of the connections ; and k, warm water from the water-
jacket of the engine is circulated through the jacket /, view (a),
of the carbureter.

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42 AUTOMOBILE CARBURETERS § 5

The carbureter is primed for starting by lifting the needle
valve i, view (6). There is no needle valve acting on the
spray nozzle, but the richness of the mixture is regulated by
adjusting the openings of the slits a, view (a). This is done
by means of a shutter surrounding the pipe in which the slits
are cut. This shutter has openings cut in it corresponding
to the slits a, and by rotating it the air passages are either
made larger or smaller. The shutter is controlled by the
operator through a lever connected to the arm m, view (6).
By partly closing the slits, the relative amount of carbureted
air is reduced and a larger proportion of air is compelled to
enter through the valve e.

There is one float-feed spray carbureter having two auxiliary
air valves, one controlled by a stronger spring than the other.
One valve admits extra air for medium speeds and the other
opens for higher speeds.

60. Compensating Sprln^less Carbureter. — In

Fig. 17 is shown a compensating type of carbureter in which
the compensating valves are controlled by the weight of balls.
At d is shown one of the five bronze balls that rest in seats
having varied angles, so designed that one ball at a time
rises as the air suction increases, giving an increasing ratio
of auxiliary air as the suction of the engine increases. The
gasoline enters at g, and the amount in the float chamber is
controlled by the float. When the float rises sufficiently,
the valve opening at / is closed by the valve to which the
weight h is fastened. The air enters at a, passes, as shown
by the arrows, through the so-called venturi-shaped air
passages 6, past the spray nozzles e toward the so-called
butterfly throttle valve c. When the suction is sufficient,
one or more of the bronze balls rise and admit more air,
which mixes with that coming past the nozzle, and the mix-
ture passes through the throttle valve c toward the cylinders.
The gasoline can pass from the float chamber through the
holes i to the spray nozzle, while the constant supply of air
from a passes on each side of this cross-web through which
the holes i are drilled.

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AUTOMOBILE CARBURETERS

This carbureter has no springs and only one adjustment —
that of the spray nozzle — which is made by the handle ;.
The proper adjustment, when secured, may be locked by the
screw k. The float chamber and gasoline inlet g may be
rotated about an axis passing through the spray nozzle, so
that the inlet can be placed in a suitable position for almost
any engine. The constant-air-supply inlet a can also be
rotated about the same axis, independently of the float
chamber, for the same purpose. When in proper position,
the parts are held tightly together by the nut /. The throttle

lever m can also be secured in almost any horizontal position,
because on its hub are teeth that mesh with corresponding
teeth forming part of the throttle valve, the two being held
together in the desired position by the capscrew n. Hence,
the throttle lever m and valve c can readily be set so that
when the throttle-control lever on the steering wheel is in
its extreme, or so-called closed, position, the engine will not
stop, but will continue to run at its slowest speed.

61. Carbureters With Air Inlet Controlled by
Tbrottle. — In addition to the automatic carbureters just
described, there is a class having the auxiliary air inlet

222—7

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AUTOMOBILE CARBURETERS

§5

rigidly connected to the throttle so that the two open and
close together. This arrangement does not secure strictly
automatic action, because the speed of the engine varies with
the load as well as with the throttle opening. Nevertheless,
it is found in many cases to give exceedingly satisfactory
results.

An early form of such a carbureter is shown in Fig. 18, (a)
being a top view and (b) a sectional side view. At a is shown
the float chamber; at 6, the spray nozzle; and at c, a spray
choking device equivalent to a needle valve, except that its
end is blunt instead of pointed; it is carried by a screw of
coarse pitch, as shown, and is raised or lowered to increase
or retard the flow of gasoline from the nozzle by turning the
screw by means of the lever d. The principal stream of air
is warmed by passing around the exhaust pipe. It enters
the annular chamber e by the pipe g, and, following the direc-
tion of the arrows, it is drawn past the spray nozzle b and up
into the branch pipe /, which leads directly to the inlet valve
chambers of the engine cylinders. The auxiliary stream of
air enters by the slot h in the tube /. Inside this tube is a
slotted shutter, or sleeve, i, with the right-hand end closed
and connected to the stem ;. When the shutter is moved to
the left or the right, it will partly cover or uncover the slot h,
and at the same time, by moving to the left, it partly obstructs
the passage and hence increases the velocity of both the
carbureted air and the auxiliary stream of air before they
pass into the pipes k and /.

In this carbureter, the spray-nozzle valve is operated in
conjunction with an air throttle. In other designs more or
less similar, the spray valve is not moved except for adjust-
ment; this baffle-plate type of spray valve is sometimes
difficult to adjust so as to obtain a suitable mixture. A
slight variation in the form of the surfaces near the spray
orifice is liable to have a very decided effect on the flow of
gasoline. The lodging of a particle of foreign matter, such
as sand or earth, or even the collecting of fine dust at the
nozzle, may so change the mixture proportions as to reduce
markedly the power of the engine, or even stop it.

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AUTOMOBILE CARBURETERS

62, In another carbureter, a by-pass controlled by a
mechanically operated throttle valve furnishes the auxiliary,
or diluting, air stream. This throttle is connected to the
main throttle, but there is also a valve controlling the entrance
of the air to the spray chamber. This valve, by lifting when
the velocity of the air increases, tends to keep the suction in
the spray chamber more nearly constant than would other-
wise be the case. Fig. 19 shows two sectional views of such
a carbureter, the two views being taken at right angles to.
each other. The intake for both the main and the diluting

Pio. 19

air streams is shown at a, view (b). The spray chamber is
greatly contracted about the spray nozzle 6, so as to give the
air a high velocity and so that the gasoline may be drawn
freely through the spray nozzle. The air valve c is shown
wide open. The auxiliary-air stream passes up through d,
view (a), past the butterfly valve e, which is controlled by
the links and levers, at /, attached to the main throttle g.
The passage of the gasoline from the float chamber to the
spray nozzle is controlled by the needle valve /i, view (6).
This valve is regulated by the operator.

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46 AUTOMOBILE CARBURETERS § 5

63. In still another type of throttle-controlled carbureter,
which can be made to operate in a very simple manner, the
spray nozzle opens upwards into the vertical pipe through
which the air passes to the engine. Two throttle valves are
placed in the pipe, one above the spray nozzle and the other
below it. The valves are mechanically connected together,
so that both can be moved in unison by the operator. They
are adjustable relative to each other in order that the proper
setting may be made to meet the requirements of the engine
to which the carbureter is attached. The aim of adjustment
is, of course, to secure a mixture of constant proportions.

GRAVITY FEED, OR FL.OATL.ESS, CARBURETERS

64. There is another class of carbureters known as
fi^ravlty-feed, or floatless, carbureters, and while many
of them have given good service, they are not in common
use. In them, the gasoHne is fed directly to the spray
nozzle from the supply tank of the engine without passing
any intervening valves for regulating its flow. There may,
of course, *be a valve, or valves, for cutting off the gasoline
supply when the engine is not running. In one type, the
vertical spray nozzle has a needle valve whose point projects
into the orifice from above. A horizontal disk is attached to
the valve stem a short distance above the nozzle. When
there is no flow of air through the carbureter, the weight of
the valve and attached parts is sufficient to keep the orifice
closed and prevent the flow of gasoline. However, when the
engine draws air upwards through the carbureter, the needle
valve is lifted by the action of the current of air against the
lower side of the disk attached to it, so that the spray orifice
is opened and gasoline comes out into the mixing chamber.
In order to insure closing of the needle valve and to prevent
the collection of dirt on the valve or spray orifice, the disk is
sometimes provided with small reed-like tongues made by
partly cutting out thin strips of the sheet metal in a circum-
ferential direction and then slightly bending up the end
of each strip. The air in striking these reeds, or strips, gives

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§ 5 AUTOMOBILE CARBURETERS 47

a rotary motion to the disk and valve, so that the latter
spins on its seat at the time of closing and thus keeps the
parts in contact free from dirt.

Other types of this class of carbureter have the spray
valve lifted by methods different from the one just described.
All of these methods depend, however, on either the suction
of the engine or the velocity of the air-current, or both.

65. Carbureters of this class seem to have found use only
on cars in which the gasoline supply tank is located at a
level higher than that of the carbureters, so that the gasoline
flows by gravity from the tank to the carbureter. The flow
of gasoline is naturally more rapid when the supply tank is
full than when it is nearly empty. Therefore, the mixture
is richer when the tank is full. If the carbureter is located
at the forward part of the car and the tank under the
driver's seat, the flow of gasoline to the carbureter will be
less rapid when the car is climbing a grade than when it is
on a level or is descending a grade.

HOT- AND COL.D-AIR INTAKES

66. Some carbureters are connected to both hot- and
cold-air Intake pipes, and are provided with stationary air
valves that can be set to regulate the proportions of hot and
cold air drawn into the carbureter. Thus, in cold weather,
the stationary valves can be set so as to draw in more hot
air than cold air. In summer, the setting can be for more
cool air. The hot-air intake generally consists of a sleeve, or
hood, that surrounds some hot part of the engine, as a portion
of the exhaust pipe or of the un jacketed part of the engine
cylinder. Some carbureters are jacketed so that hot water
from the engine cylinder passes around the mixing chamber,
as shown in the illustrations of some of the carbureters
already described.

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§ 5 AUTOMOBILE CARBURETERS 49

CARBURETER CONNECTIONS

67. In Fig. 20 is shown the gravity-feed gasoline tank,
the auxiliary tank, the water-jacketed, automatic air-valve
carbureter, and the necessary piping of a large automobile.
The auxiliary tank b is built in the top of the main gasoline
tank a. The gasoline in the main tank is used when the
valve handle c is turned down to coincide with the main-tank
supply pipe, and that in the emergency tank is used when
the handle c is turned up to coincide with the emergency-
tank supply pipe. When the handle c is in the position shown,
it shuts off the supply from both tanks. Should the supply
from the main tank become exhausted, the gasoline in the
auxiliary tank may be used. Furthermore, in climbing
extraordinarily steep grades with the main tank partly
filled, the elevation of the front end of the car, due to the
grade, may not permit the gasoline in the main tank to
reach the carbureter. By opening the valve to the auxiliary
tank, its higher position insures a gasoline supply to the
carbureter.

A gasoline filter d is located between the gasoline tank and
the carbureter. To drain and clean this filter, the valves c
and e are closed, the sediment tube / is removed and cleaned,
and a small quantity of gasoline is allowed to flow from the
carbureter or from the tank if not enough will come from the
carbureter to clean the strainer. This strainer consists of a
circular piece of fine-mesh wire gauze of sufficiently large
area to permit an ample supply of gasoline to pass through
it. The gasoline enters the lower part of the strainer, passes
upwards through the wire gauze, and then to the carbureter.
Hence, particles of dirt and water tend to fall off the gauze
strainer into the sediment tube, because the area of the gauze
is large and the gasoline velocity small. All the gasoline
piping is large, namely, A i^ch in diameter, so that there is
little chance of clogging. The filler cap g is large and may
be removed by ^ of a revolution. Both tanks are filled
from the one opening. The carbureter can be drained by
closing the valve c and removing the sediment chamber /.

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50 AUTOMOBILE CARBURETERS § 5

68. Entering the carbureter, the gasoline first passes
through the float chamber h, where its level is controlled
by the float. As the float rises, it actuates two balance
levers at the top of the chamber and pushes down the
plunger in the center, thus closing the needle-valve gasoline
inlet at the bottom. The gasoline then passes from the
float chamber to the mixing chamber through the inclined
spray nozzle. The main air supply enters the mixing
chamber through a valve i below the spray nozzle. The
amount of air that can enter this way is controlled by a
lever that is mounted on the dash of the car and suitably
connected to rod ;. By means of this lever, the slots in
the air-inlet valve may be made to coincide gradually with
the slots on the bottom of the air chamber. The air enter-
ing through this main-supply opening passes by the spray
nozzle into the mixing chamber above, where more air may
enter through the auxiliary air valve k. The mixture passes
through the throttle valve / and the inlet manifold m to
the cylinders.

The quantity of mixture that enters the cylinders is
regulated by the cone-shaped, double-seated throttle valve,
which is operated by the rod w connected to the engine
governor, the accelerator pedal, and the throttle lever on the
steering wheel. Ordinarily, the throttle lever controls the
speed of the engine, unless its speed becomes what the
makers consider excessive; then, the governor automatically
controls the throttle lever to prevent this condition. How-
ever, should the operator desire a higher engine speed than
he can obtain with the hand-throttle lever, he. can cut out
the engine governor by pressing the accelerator pedal. He
is not likely to press this pedal very long at one time, how-
ever, as he must keep his foot on it to do so. The cone-
shaped throttle valve has slots through it at n, so that a cer-
tain amount of mixture can always pass through; but when
the valve moves to the right, the seat at v is opened more
and more and that at p is also farther opened. To prime
the carbureter, the small brass cap u must be taken off and
the rod under it lifted.

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§ 5 AUTOMOBILE CARBURETERS 51

69. The mixing chamber o is jacketed, and water from
the engine jacket flows through the pipe q r, the carbureter
water-jacket, the connection s, and the pipe /, to the radiator x.
Thus, the mixture is warmed after the engine has run long
enough to warm the water. The following objection applies
to all water-jacketed carbureters, however: When heat is
most needed, as in starting the engine on a cold day, there is
none available. A carbureter warmed by exhaust gases from
the engine cylinder warms quicker — a few explosions only
may be necessary — but such a carbureter is very apt to be
overheated most of the time. If the pipe conveying the hot
gases to the carbureter are small enough to prevent over-
heating of the mixture, they become too easily clogged up
with soot and carbon. If a carbureter is to be heated, the
heat should be applied as close as practicable to the spray
nozzle, or even below it, so that the air passing the nozzle
will be heated.

CARBURETER REGUIJ^TION AND ADJUSTMENT

70. Practically all carbureters for automobile use are of
the constant-level type. The gasoline passes from the tank
through a needle valve to a constant-level chamber, in which
the level of the gasoline is controlled by a float that acts on
the needle valve, closing it when the level reaches the outlet
of the spray nozzle. In this way, the rate of gasoline feed
to the spray nozzle is determined solely by the degree of
vacuum existing in the mixing chamber, as is also the velocity
of the air stream, irrespective of the amount of gasoline in
the tank. The combined influence of the vacuum in the
mixing chamber and the velocity of the air stream is to
make the mixture richer when the engine is running fast and
the throttle is wide open than it is when the engine is run-
ning slowly with open throttle, or fast with the throttle
partly closed. In the first case, there is considerable vacuum
and a high velocity of the air, while in either of the other
two cases there is less vacuum and a smaller velocity of the
air. This is because the throttle is located between the
carbureter and the engine, and not at the* carbureter intake,

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52 AUTOMOBILE CARBURETERS § 5

so that, whatever the vacuum between the throttle and
the engine may be, the vacuum in the carbureter itself
is so reduced by the throttle valve that only the amount
of air required by the engine will be drawn in at each stroke.
The vacuum between the throttle and the engine has no
effect on the amoimt of gasoline vaporized; this depends
only on the speed of the air that is drawn through the
carbureter.

The rate at which the gasoline is drawn from the spray
nozzle is affected by both the vacuum and the air velocity
more than it would be by either separately, so that, when
neither is restricted, too much gasoline is evaporated. It is
desired to keep the flow of gasoline as nearly as possible
proportional to the velocity of the air, and in order to
accomplish this result, the newest forms of automatic carbu-
reters restrict either the velocity of the air stream or the
vacuum in the carbureter as the demands of the engine
increase.

71. A carbureter may deliver either too rich a mixture
or too weak a mixture at all speeds within the range of
operation of the engine. More often, however, a mixture will
be rich at certain speeds, high or low, and either normal or,
possibly, too weak at other speeds; or it will be weak at high
or low speeds and normal or too rich when the speed is
changed. Owing to the large number of types of carbu-
reters, no definite rules that will apply to all can be made
for their adjustment. If the printed instructions of the
maker are at hand, they should be followed. If these should
fail to give the desired result, an observance of the following
general principles may aid in correcting the trouble:

1. A non-automatic carbureter will tend to take propor-
tionally more gasoline at high than at low speeds. If
adjusted correctly for low speeds, it will be wrong for high
speeds, and vice versa.

2. A needle valve acting on the spray nozzle does not
produce automatic regulation; it reduces or increases the
gasoline feed in substantially the same ratio for all speeds.

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§ 5 AUTOMOBILE CARBURETERS 53

3. A fixed shutter over the air intake does not produce
automatic regulation. By partly closing it, the suction in
the spray chamber is increased and the amount of air sup-
plied is reduced, thereby increasing the richness while redu-
cing the volume of the charge.

4. To obtain a uniform mixture with a carbureter that
is not automatic, the gasoline feed at high speeds must be
restricted, or the air must be allowed to enter more freely,
to diminish the suction in the spray chamber. Some car-
bureters are arranged to by-pass a portion of the air around
the spray chamber at high speeds. Sometimes the by-pass
valve controlling this action is connected to and controlled
by the throttle lever.

5. In an automatic carbureter, opening the needle valve
or reducing the air-intake opening will give a richer mixture
at all speeds.

6. In an automatic carbureter, reducing the spring ten-
sion on the auxiliary, or diluting, air valve will permit this
valve to open wider, especially at high speeds, and will
therefore make the mixture weaker at high speeds. The
same principle holds good regarding the spring tension on
such a device as the head or thimble, shown in Fig. 15, that
permits a portion of the air to pass around the spray chamber.
Increasing the spring tension on the auxiliary air valve makes

'the mixture richer at high speeds.

7. A weaker mixture may be obtained at low speeds by
increasing the spring tension on the automatic or auxiliary
valve and enlarging the main air intake ; or it may be obtained
by increasing the spring tension and partly closing the
needle valve. The latter arrangement will not give as full
charges as the other, as the resistance to the ingoing charge
will be greater; but if the carbureter is large for the engine,
it may give better vaporization on account of the higher air
velocity past the spray nozzle.

8. If, at high speed, richer charges are desired, the throt-
tling effect or reduction of air supply due to increasing the
spring tension on the automatic valve may be offset by
increasing the opening of the main air intake so as to

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54 AUTOMOBILE CARBURETERS § 5

increase the velocity of the air flowing past the nozzle and
thus draw therefrom an increased quantity of fuel. The
needle valve also should be opened farther, to avoid the
necessity of restricting the automatic valve unduly. At low
speeds, the increased openings of the main intake and the
needle valve will neutralize each other as regards the pro-
portions of the mixture.

9. If the automatic valve is provided with a stop; its
effect will be to render the carbureter non-automatic at
speeds above those at which the automatic valve comes
against the stop. For this reason, reliance should be placed
on the spring where possible, rather than on the stop. The
chief function of the stop should be to prevent the valve
from opening under sudden pulsations so far that, by reason
of its inertia, it cannot close promptly.

10. A slightly weak mixture bums faster than a normal
or a rich mixture. This, therefore, is the best mixture for
high speeds. When, however, the engine is working under
a heavy load, a slow-burning mixture is better, as it main-
tains a higher pressure on the working stroke. The ideal
carbureter adjustment, therefore, should give a normal mix-
ture, or one very slightly rich, at the slowest speeds, and a
weaker mixture at high speeds.

11. Occasionally, a change in carbureter adjustment is
made necessary by a change in weather or in the quality of*
the fuel. Such changes are properly made in the main air
or needle-valve openings, since the changes must be the
same for all speeds.

12. In order to have correct adjustment, the gasoline
level in the float chamber must be at the spray orifice or
slightly below it.

72, Adjustment of New Carbureter. — In adjusting a
new carbureter, the first thing to do is to see that the gasoline
level is at the right height, which it probably is. If not,
examine the float to see that it is working properly and is set
correctly. Next see that the igniting device produces a good .
strong spark, and then follow the instructions of the maker

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§ 5 AUTOMOBILE CARBURETERS 55

regarding the setting of the needle valve, main air intake,
and automatic valve. Prime the carbureter freely, and start
the engine. Run it throttled to about half speed at first,
with suitable spark lead, and gradually reduce the opening of
the needle valve, a little at a time, until the engine shows
signs of running weaker. Then open it to the point where
the engine runs best. If the engine starts, but will not keep
on running, it is getting either too much or too little gasoline,
probably the latter. The former will be indicated by black
smoke in the exhaust, and probably a very loud exhaust due
to slow combustion. If there is no black smoke, but the
engine will not run, try increasing the needle-valve opening,
a little at a time, until the eng^e runs steadily, after which
adjust as before.

Now open the throttle a little, and note the result as the
engine runs up to or a little beyond its maximum speed. If
it weakens, it is probably getting too much gasoline. Relax
the spring on the automatic valve, and try again. Watch
for black smoke, but remember that this appears only when
the excess of gasoline is considerable. If necessary, open
the needle valve and readjust the main air intake. Try also
closing the throttle until the engine barely runs, retarding
the spark, and note how quickly it responds as the throttle
is opened. A little further experimenting along the lines
just indicated will result in an adjustment sufficiently cor-
rect to allow the engine to be run in regular service, after
which it is comparatively easy to discover what changes will
produce the best mixture.

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ELECTRIC IGNITION

(PART 1)

THEORY AND APPLICATION

EliEMENTARY PRlNCIPIiES

DEFINITIONS OF BL.ECTRICAL. TERMS

1. Electricity is the name given to the cause of all
electric phenomena. The exact nature of electricity is not
known; but its effects, the laws governing its action, and the
methods of controlling and using it are well understood. Elec-
tricity is neither a form of matter, as matter is generally under-
stood, nor is it a form of energy, although energy is required
to move it, and when in motion it is capable of doing work.

2. Electricity may manifest its presence or movements
in various ways. For example, it may cause attractions or
repulsions of some kinds of matter; it may decompose into
elements some kinds of matter through which it passes, as
the decomposition of water into two gases, hydrogen and
oxygen; it may cause a magnetic needle to deflect; it may
cause physiological effects in or shocks to the nervous sys-
tems of all animals; it may heat substances through which
it passes; or it may pass through air in the form of an electric
spark, or arc.

3. Electricity may appear either to reside on the surface
of bodies as a cliaripre, or to flow through the substance or

eorrmoHTiD by international textbook company, cntcrcd at stationcrs* hall, London

§6

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2 ELECTRIC IGNITION § 6

on the surface of a body as a current. That branch of the
science which treats of charges on the surface of bodies is
termed electrostatics, and the charges are said to be electro-
static, or simply static, charges of electricity. Electrodynamics
is that branch of science which treats of the action of electric
currents.

4, Electrostatics. — For present purposes, very little
need be said about electrostatics. The electricity used
for igniting the combustible mixture, or charge, in auto-
mobile engines is in motion, and hence its discussion falls
naturally under electrodynamics.

5. Conductors and Insulators. — All bodies
conduct electricity to some extent, and there is no known
substance that does not offer some resistance to its flow.
All bodies have been divided into two classes: non-con-
ductors, or Insulators, which offer a very high resistance
to the passage of electricity; and conductors, which
offer a comparatively low resistance to the passage of
electricity.

All metals and alloys allow electric current to pass through
them readily, but some offer much greater resistance to the
flow of the current than do others. Some of the non-metallic
substances also allow the current to pass quite freely, but
offer much greater resistance than do the metals. A sub-
stance that allows current to pass freely is called a good
conductor of electricity and its conductivity is said to be high.
The classification of substances as conductors depends to
some extent on the nature of the sendee for which they are
to be used.

In automobile practice, the following substances are used
as conductors: Copper in wires, switches, and parts of
apparatus; brass and bronze in parts of apparatus and
machinery ; iron and steel as parts of the machinery ; aluminum
alloy in machine parts; tin-foil in connection with induction
coils; platinum or an alloy of platinum and iridium (platino-
iridium) for the points at which the electric spark occurs in

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§ 6 ELECTRIC IGNITION 3

igniters; and the metals, carbon, and alloys, and also solutions,
in batteries.

6. Copper is a far better conductor than any other of the
substances mentioned. Pure aluminum has about 63 per
cent, of the conductivity of copper, but the aluminum alloys
used probably seldom have more than one-eighth of the
conductivity of copper when dimensions, and not weights,
are compared. The softer irons and soft, or mild, steels
do not have more than about one-eighth of the conductivity
of copper. The hard steels have much less. The brasses
and bronzes probably never exceed one-third of the conduc-
tivity of copper.

Moist earth is a sufficiently good conductor of electricity
to cause trouble when it collects as damp dust around parts
between which the current should not pass.

7. An insulating: substance is one that does not
allow any appreciable quantity of electricity to pass through
it under the condition in which it is used. The insulating
materials commonly used for the electrical parts of an auto-
mobile are: India-rubber composition; silk, and cotton on
wires, used in apparatus and for connecting them; paraffin
in induction coils and to some extent on wires; hard, or
\nilcanized, rubber in induction coils, magnetos, etc.; wood
fiber (vulcanized or compressed into hard sheets, tubes, etc.)
in the electric apparatus and around wires; mica, porcelain,
and steatite, also called soapstone, in the spark plug; shellac
applied as a varnish on wood and in some parts of the appara-
tus; dry wood, varnished; paper, varnished, in induction
coils; pitch in dry batteries, and sometimes on wire.

Enamel, glass, slate, and marble are good insulators,
but they are not much used on automobiles. Dry air is
an excellent insulator. Oils are also good insulators, but
they are not intentionally used as such on automobiles.
The timer or commutator, which forms a part of the electrical
circuit, is usually filled with grease or oil. Neither grease
nor oil could be used for lubricating purposes in such a way if
they were good conductors.

222—8

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4 ELECTRIC IGNITION ^6

8. Resistance . — The opposition that a substance
offers to the passage of a direct current through it is called
its resistance. If the sectional area of a piece of a given
material is uniform, its resistance is directly proportional to
its length. Hence, a piece of copper wire of uniform diameter
and 10 feet long has twice the resistance of 5 feet of the
same wire; also a piece 15 feet long has three times the resist-
ance of 5 feet of the same wire.

If the lengths of two pieces made of similar material are
equal, their resistances are inversely proportional to their
sectional areas. The greater the sectional area, the less the
resistance. Thus, the resistance of 1,000 feet of No. 13
copper wire, which has a sectional area of .004067 square
inch, is 1.999 ohms; whereas, the resistance of 1,000 feet of
No. 10 copper wire, which has a sectional area of .008154
square inch, or a trifle over twice the sectional area of the
No. 13 wire, is .9972 ohm, or very nearly half that of
the No. 13 wire. Annealed, soft-copper wire insulated with
cotton, silk, rubber, or composition of some kind, is about
the only wire used in the electrical circuits of automobiles.

ELECTRODYNAMICS

9. Electric Potential. — The electric potential of a

body is its electrical condition, and is analogous to pressure
in gases, head in liquids, and temperature in heat. If the
liquids of each of two connected vessels have the same head,
there will be no flow from one to the other ; but if the liquid in
one of the vessels has a higher head than that in the other,
there will be a flow corresponding to the difference of the
heads. Similarly, if two - connected bodies have the same
electrical potential, there will be no flow of electricity from one
to the other; but if one has a higher potential than the other
— that is, if there is a difference of electrical potential — electric-
ity is said to flow front the body having the higher potential to
the body having the lower potential, and the rate of flow is
proportional to the difference of potential.

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§.6 ELECTRIC IGNITION 5

10. The earth may be regarded as a reservoir of elec-
tricity of infinite quantity, and its potential, or pressure, may
therefore be taken as zero. For convenience, it has been
arbitrarily asstmied that the electrical condition called positive
is at a higher potential, or pressure, than the earth, while
that called negative is at a lower potential, or pressure, than
the earth ; and that electricity tends to flow from a positively
to a negatively electrified body. Therefore, when a posi-
tively electrified body is connected by a conductor to the
earth, electricity is said to flow from the body to the earth;
and, conversely, when a negatively electrified body is con-
nected to the earth, electricity is said to flow from the earth
to the body. Also, when a positively and a negatively
electrified body are connected by a conductor, electricity is
said to flow from the positively electrified body to the body
having the negative charge. While these assumptions may
or may not be true, they assist very materially in explaining
and understanding the subject of electricity.

11. Electricity is a condition of matter, and not matter
itself, as it has neither weight nor dimensions. Consequently,
the statement that electricity is flowing through a conductor
must not be taken too literally ; it is only another way of say-

• ing that a change, the nature of which is not fully understood,
is taking place in the electrical condition of the conductor
and that differences of potential are tending to become equal-
ized. It must not, therefore, be supposed that any substance,
such as a liquid, is actually passing through the conductor
in the same sense that water flows through a pipe.

12. Electromotive Force. — The expression electro-
motive force, usually abbreviated to E. M. F., has

practically the same meaning as difference of electric poten-
tial, or electric pressure. Electromotive force is the force
that moves or tends to move electricity from one place to
another. The practical unit of electromotive force is the
volt. An instrument used to measure electric pressure and
indicate its intensity in volts is called a voltmeter.

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6 ELECTRIC IGNITION J 6

13. An electromotive force may be produced or gener-
ated in a number of ways, among which are the following:

1. By friction and electrostatic induction.

2. By dipping the ends of two strips of dissimilar mate-
rials into a liquid that has a greater tendency to act chemic-
ally on one material than on the other. The electromotive
force is due to chemical action or affinity between the strips
and the liquid.

3. By magnetic induction. The explanation of this
method will be made after the subject of magnetism has
been considered.

4. By the contact of two dissimilar materials, as shown
in Fig. 1, when the junction J is at a different temperature

; from the two ends a and fe,

I Copper I Iron | which are supposed to be at

the same temperature. An
*^" ^ electromotive force produced

in this manner is called a thermoelectromotive force.

The production of an electromotive force by friction is
made evident by the charges of electricity accumulated on
large moving belts. The production of electromotive forces
by the first and fourth methods is not of great importance
in this discussion, and will not be referred to again.

14, Ampere, Volt, and Olun, — The chemical action
in a galvanic cell produces an electromotive force, and this,
in turn, causes a difference of electric pressure, or tension,
at the terminals of the cell. This difference of electric
pressure, or potential, commonly called pressure, causes a
current to flow when the external circuit is closed. Both the
external circuit and the internal circuit offer resistance to
the flow of the current. The forcing of the current through
the wire of the external circuit produces heat in the wire.
If the terminals of a dry battery are connected by a thin,
insulated magnet wire wound in a coil, as by winding the
wire on a spool, such as is used for silk thread, the coil will
become decidedly warm in a ^J^rt time. There would be
as much heat developed in the wire if it were not coiled, but

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§ 6 ELECTRIC IGNITION 7

it would keep cooler on account of being more exposed to the
atmosphere.

Electric pressure is measured in volts; current in amperes;
and the electrical resistance in dims. A pressure of 1 volt
will send a current of 1 ampere through a resistance of 1 ohm ;
also 2 volts will send 2 amperes through the same resistance.

An instrument that indicates the number of amperes of
current flowing in a circuit in which it is connected is called
an ammeter. For use in automobile practice, an ammeter
and a voltmeter are frequently combined in a single small
case that is easy to handle.

15. Ohm's liaw. — The relation between the three
factors — resistance, electric pressure, and current — is
expressed by Ohm's law. If the values of any two of
these factors are known, that of the third may be calculated
by the following rules:

Rule I. — The strength, in amperes, of a direct current
flowing in a closed circuit, when the electromotive force and
the total resistance are known, is found by dividing the electro-
motive force, in volts, by the total resistance, in ohms; that is,

, . electromotive force in volts

current m amperes =

resistance in ohms

Rule II. — The total resistance of a closed circuit, in ohms,
when the electromotive force and the direct current are known,
is found by dividing the electromotive force, in volts, by the
current, in amperes; that is,

. , electromotive force in volts

resistance m ohms = — -

current in amperes

Rule III. — The total electromotive force, in volts, expended
in a closed circuit, when the direct current and the total resist-
ance are known, is found by multiplying the current, in amperes,
by the total resistance, in ohms; that is,

electromotive force in volts = current in amperes
X resistance in ohms

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8 ELECTRIC IGNITION § 6

16. The following examples show the application of
Ohm's law.

Rule I determines the strength of current that will flow
in a conductor of a given resistance when the pressure, in
volts, is known.

Example 1, — A circuit has a resistance of 45 ohms and an available
pressure of 15 volts; what is the strength of the current in amperes?

Solution. — According to rule I, the current is equal to 15 divided
by 45, which is J ampere. Ans.

Example 2. — What current can be made to flow through a circuit
having a resistance of 10 ohms, if an electromotive force of 15 volts
is applied ?

Solution. — According to rule I, current = 15 -^ 10= 1^ amperes.

Ans.

17. In case the electromotive force, or difference of
potential, is known, rule II must be used to calculate the
resistance of the circuit that will allow a given current to
flow through it.

Example 1. — The electromotive force of a circuit is 100 volts; it is
desirable to have a current of .5 ampere flowing in the circuit; what
should be the resistance?

Solution. — According to rule II, the resistance is equal to 100
divided by .5, which is 200 ohms. Ans.

Example 2. — Through what resistance can an electromotive force
of 50 volts cause a current of 5 amperes to flow?

Solution. — According to rule II, the resistance = 50 -^ 5 -= 10 ohms.

Ans.

18. To find how much pressure it will require to force a
given current through a given resistance, it will be necessary
to use rule III.

Example 1. — How much pressure will it take to force a current of
1.8 amperes through a resistance of 5 ohms?

Solution. — According to rule III, the voltage required is equal
to 1.8 multiplied by 5, which is 9 volts. Ans.

Example 2. — What voltage is required to send a current of
25 amperes through a resistance of 4 ohms?

Solution. — According to rule III, the difference of potential
required = 25 X 4 = 100 volts. Ans.

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ELECTRIC IGNITION

THE VOLTAIC CELL.

19. If two dissimilar materials, as zinc and copper or
zinc and carbon, are partly or wholly immersed in water
in which some acid has been mixed or a salt has been dis-
solved, and are connected by a conductor outside the liquid,
chemical action will occur between the two materials and the
liquid, and an electric current will flow through the liquid
and the external circuit. Such a device is known as the
voltaic, or galvanic, cell, from its discoverers, Volta
and Galvani.

20, Fig. 2 shows a glass vessel A containing water, in
which a salt commercially known as sal ammoniac (chemic-
ally known as ammonium chlo-
ride, or chloride of ammonia)
has been dissolved. At C is
shown a slab of carbon, or coke,
compressed to dense form, and
at Z, a metal plate of zinc.
A copper wire is firmly attached
to the carbon slab and also
to the zinc plate, so as to be
in intimate contact with the
material. If the free ends of
the wires are brought together,
and are clean, so as to make good metallic contact, a current
of electricity will flow from the carbon plate through the
wires to the zinc plate, and from the zinc plate through the
liquid to the carbon plate. The arrows show the direction
of current flow when the ends of the wires are connected
together.

The liquid, no matter what its composition may be, is
called the electrolyte, and it must be such that it will
act more readily on one plate than on the other, in order to
produce a difference of potential, or electromotive force,
between them. The resistance of the two plates and the
electrolyte is called the Internal resistance of the cell.

Fio. 2

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10 ELECTRIC IGNITION § 6

The points where the wires are attached to the plates
outside the liqiiid are the terminals. The one at the
carbon slab is the positive terminal, or electrode,
and is indicated by the plus sign (-f ); and the one at the
zinc plate is the ne^rative terminal, or electrode, and
is indicated by the minus sign ( — ).

21. The equalizing flow that is constantly taking place
from one plate to the other is known as a direct current
of electricity, and is one that always flows in the same direc-
tion. An alternating^ current, on the other hand,
is one that changes the direction in which it flows in a con-
ductor regularly a definite number of times per second.
Alternating current is not produced by chemical action, but
is generated by mechanical means.

CIRCUITS

22. An electric circuit is a path composed of a con-
ductor or of several conductors joined together, through
which an electric current flows from a given point around the
conducting path back again to its starting point. A circuit
is broken, or open, when its conducting elements are dis-
connected in such manner as to prevent the current from
flowing. A circuit is closed, or complete, when its con-
ducting elements are so connected as to allow the current to
flow. A circuit in which the conductors have come into con-
tact with the ground, or with some electric conductor leading
to the ground, is said to be a grrounded circuit, and the
contact is called an earth, or a in*ound. In automobile
practice, a grounded circuit is one that is completed through
the engine and frame of the car, the wire connected to the
frame or engine being called the grounded connection, even
though there is no connection whatever with the earth.

The path of the current through the wires outside of the
cell shown in Fig. 2 is the external circuit, and that
through the cell from terminal to terminal is the internal
circuit. If any electrical apparatus is connected into

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§ 6 ELECTRIC IGNITION 11

the external circuit, so that the current must pass through it,
the apparatus forms a part of the external circuit. A circuit
divided into two or more branches, each branch transmitting
part of the current, is a divided circuit; the conductors
forming these branches are said to be connected in parallel,
or multiple. Each branch taken separately is called a sliunt
to the other branch or branches.

23. Resistance and Voltagre of a Cell. — The vol-
taic, or galvanic, cell itself offers internal resistance to the
flow of current through it. This resistance must be taken
into account when calculating the current, if the internal
resistance is appreciably great in proportion to the external
resistance of the circuit. The resistance of dry cells varies
greatly, but the usual form of cell, which is 2^ in.X6 in.
in size, generally has a resistance not exceeding .4 ohm,
provided it is in good condition and is not too old. The
internal resistance of the cell causes the difference of potential
at its terminals to decrease as the current in the external
circuit increases. The voltage across the battery terminals
is therefore less than when the circuit is open and the cell
idle.

The voltage of a dry primary cell with carbon and zinc
elements varies from 1.3 to 1.6 on open circuit. When the
external circuit is closed and the current is flowing, the
pressure drops. The greater the amount of current delivered
by the cell, the greater is the drop in pressure.

EXAMPLES FOR PRACTICE

1. The total resistance of a closed circuit is 23 ohms. If the
current is 1.4 amperes, what is the total electromotive force in volts?

Ans. 32.2 volts

2. A difference of potential of 1 1 volts exists between the terminals
of a conductor whose resistance is 20 ohms. Find the current flowing
through the conductor. Ans. .55 ampere

3. A circuit has an available pressure of 20 volts. What is its
resistance if a current of 3 amperes can flow through it?

Ans. 6 J ohms

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12 ELECTRIC IGNITION § 6

MAGNETS AND MAGNETISM

NATURAL MAGNETS

24. Near the town of Magnesia, in Asia Minor, the
ancients found an ore that possessed a remarkably attractive
power for iron. This attractive power they named ma^irnet-
ism, and a piece of ore having this power was termed a
mag^net. The ore itself has since been named magnetite,
and in early times was found to have the peculiar property
of swinging, when freely suspended, so that the same end
always pointed toward the north. Owing to this fact, ships
could be steered in any desired direction by its aid, because
one end of a small piece of the stone so suspended would
always point to the north. From this fact, the name lode-
stone (meaning leading stone) was given to the natural ore.

ARTIFICIAL MAGNETS

25. When a bar or a needle of hardened steel is rubbed
with a piece of lodestone, it acquires magnetic properties
similar to those of the lodestone without the latter losing any
of its magnetism. Such bars are called artificial ma^irn^ts.

Artificial magnets that retain their magnetism for a long
time are called permanent ma^^nets. A piece of hardened
steel can also be more or less permanently magnetized by

rubbing it lengthwise with a pennanent magnet. The com-
mon form of permanent magnet is a bar of steel bent in the
shape of a horseshoe and then hardened and magnetized.
A piece of soft iron called an armature, or keeper, is
placed across the two free ends to prevent the magnet from
losing its magnetism.

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§ 6 ELECTRIC IGNITION 13

26. If a bar magnet is dipped into iron filings, the filings
will be attracted toward the two ends and will adhere there in
tufts, as shown in Fig. 3, while toward the center of the bar,
half way between the ends, there is no such tendency. That
part of the magnet where there is no apparent magnetic
attraction is called the neutral region, and the parts around
the ends where the attraction is greatest are called poles.

27. If the north pole of one magnet is brought near the
south pole of another magnet, attraction takes place; but if
two north poles or two south poles are brought together,
they repel each other. In general, like magnetic poles repel
each other and unlike poles attract each other.

28. The earth is a great magnet whose magnetic poles
coincide nearly, but not quite, with the true geographical
north and south poles. By the laws of attraction and repul-
sion just given, it is seen, therefore, why a freely suspended
magnet will always point in a north-and-south direction, as
in the case of the magnetic compass, which consists of a
magnetized steel needle resting on a fine point so as to turn
freely in a horizontal plane. The north-seeking pole of a
magnetic needle or other magnet is known as a north pole
though of opposite polarity to the north pole of the earth;
and the opposite end of the magnet is called a soiitli pole.
If it were customary to do so, it would be more correct to
call the north-seeking pole a south pole, or to call the earth's
north pole a south pole. It is impossible to produce a magnet
with only one pole. If a long bar magnet is broken into
any number of parts, each part will still be a magnet and have
a north and a south pole.

29. All magnetic substances are not necessarily magnets;
nevertheless, they are capable of being attracted by a magnet.
A piece of soft iron will be attracted toward either pole of
a magnet; but when not in the vicinity of a magnet it has
no defined poles, nor will it attract another piece of unmag-
netized iron.

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ELECTRIC IGNITION

§6

30. Magrnetic Lilnes of Force. — If a sheet of paper is
laid over a bar magnet, and fine iron filings are sprinkled on
the paper, the filings will arrange themselves in curved lines
extending from the north to the south pole, as shown in
Fig. 4, in which N S is the bar magnet. If the magnet is
placed in a vertical position with the paper over one end,
the filings will arrange themselves in lines extending radially
in all directions from the pole A^, as shown in Fig. 5. These
invisible lines of ma^rnetic force or simply lines of
force, acting in the directions shown, make up the mag-
netic field of a magnet, or the surrounding space in which

Fig. 4

Fig 5

magnetic substances are acted on by the magnet. The lines
of force as a whole may be referred to by any of the expressions
magnetism, magnetic induction, or magnetic flux.

31 • The direction of tUe linen of force is assumed to
be from the north to the south pole through the air or other
surrounding medium, and from the south to the north pole
through the magnet, thus completing the magnetic circuit.
Lines of force can never intersect one another. In the
magnet the lines are crowded closely together; but, as soon
as they leave the magnet, they separate as widely as possible
at the north pole and converge again at the south pole,
as shown in Figs. 4 and 5. The magnetic density is
therefore greatest in or near the iron, and decreases as the
distance from the magnet increases.

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§6

ELECTRIC IGNITION

32, The permanent magnets iised in magneto generators
are generally U-shaped, as shown in Fig. 6. The magnetic
field is much stronger in the space between the poles than
in any other region outside o^ the magnet itself. The direc-
tion of the magnetic lines of force is indicated by the dotted
lines and arrowheads.

By placing an iron keeper between the poles of the magnet,
as shown in Fig. 7, the magnetic flux will be confined to the
iron keeper, which offers less resistance, or reluctance, to the

.'V ,^--*-~.

5^^f^

|r?^grg$^ l

Pig. 6

Fig. 7

magnetic flux than does the air, and few or no lines of force
will pass through the surrounding air.

33. The only useful magnetic materials are iron and
steel. The latter is, of course, made up chiefly of the element
iron. Therefore, the presence of a piece of any other material,
such as copper, brass, bronze, tin, zinc, wood, rubber, etc.,
in the magnetic field will not change the direction of the lines
of force or the intensity of the magnetic flux. It should

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ELECTRIC IGNITION

§6

be remembered that commercial sheet tin is made of iron or
steel coated with tin, and that some forms of wire and rod
that appear like other metals on the surface, are iron or steel
coated with the other metal.

EL-ECTROM AG NETS

34. If a piece of copper wire wrapped with cotton or silk
thread is wound around a wire nail, and the ends of the
wire are connected to the cell or battery terminals, as shown
in Fig. 8, evidence that a current of electricity is flowing
through the wire will be given by the nail becoming a magnet
that will attract and hold small pieces of soft iron, such as
iron filings, or even small iron tacks. If the current is

Fio. 8

broken when a tack is hanging to the magnetized nail, the
tack will drop off because the nail then ceases to be a magnet,
or at least a magnet strong enough to hold the tack. When
the circuit is again closed, the nail will again hold the tack.
The coil of wire together with the electrically magnetized
nail form what is known as an electromagnet. The
wire winding is called the magnetizing:, or exciting coil,
and the iron or steel (nail in this case) is the core. One
end of the nail will be a north magnetic pole and the other
end a south magnetic pole.

An electromagnet loses nearly all its magnetism as soon
as the current ceases to flow. A small amount, known as
residual magnetism, is usually retained, the amount
retained being greater in cores of steel or hard iron than
in soft ones.

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§6

ELECTRIC IGNITION

35. Solenoid. — ^When a conductor is bent into a long
helix of several loops, forming a solenoid, as shown in
Fig. 9, and a current is sent through it in the direction indi-
cated by the small arrows at the ends of the conductor, the
magnetic flux will thread
through the entire solenoid,
entering at one end and
passing out at the other,
as indicated by the long
arrows. The solenoid then Fio. 9

possesses a north and a south pole, a neutral region, and all
the properties of attraction and repulsion of a magnet.

36. The polarity of a solenoid, when carrying a cur-
rent, that is, the direction of the lines of force that thread
through it, depends on the direction in which the conductor
is coiled and the direction of the current in the conductor.

To determine the polarity of a solenoid, knowing the
direction of the current, the following rule may be applied:

Rule. — In looking at the end of a helix, if the current circu-
lates in a clockwise direction, the end next to the observer is a
south pole; if it circulates in the other, or counter -clockwise ,
direction, the end next to the observer is a north pole.

Fig. 9 illustrates the first condition mentioned in the rule.

With the position of the
observer and the direc-
tion of the current as
indicated, the end to-
ward the observer is the
south pole 5 and the
other end is the north
pole N,

37. Around a solen-
oid the lines of force
^G- 10 make complete mag-

netic circuits, exactly the same as around a bar magnet.
Fig. 10 shows the direction of the invisible lines of force

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ELECTRIC IGNITION

§6

around a solenoid 5. As shown, the lines enter at a, leave at 6,
and complete the circuit through the surrpunding medium.
The current that magnetizes the solenoid, that is, the exciting
current, is supplied by the battery B.

38, Horseslioe Electromagrnet. — Fig. 11 shows the

general form and construction
of a horseshoe electro-

ma^irnet. A soft-iron bar is
bent into a U shape, leaving
two straight sides on which the
magnetizing coils are wound.
The coils must be so wound
that the current will flow around
the cores in opposite direc-
tions, as shown by the curved
arrows in the end view; this will
make one core a north pole N
and the other a south pole 5.
The part of the iron bar con-
necting the cores at the back end is called the yoke of
the magnet.

Fig. U

EliECl^OMAGNETIC INDUCTION

39. Electromagrnetlc induction is the production
of electromotive forces in a conductor or a number of con-
ductors by relative motion between the conductors and a
magnetic field in their vicinity. The strength of an induced
electromotive force is proportional to the quickness of the
relative motion and to the strength of the magnetic field;
that is, the more quickly the motion or the stronger the field,
the higher is the induced electromotive force.

40. Fig. 12 shows the method of performing a simple
experiment to illustrate electromagnetic induction. A coil
of wire a, large enough to allow a solenoid h to be readily
inserted into it has its ends c and d wound a few times around
a compass e and joined together. The magnetizing or exci-

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§6

ELECTRIC IGNITION

ting current for the solenoid b is supplied by the battery /
through the wires g and h. When the solenoid b is thrust into
the coil a or withdrawn from it, the needle of the compass is
deflected, showing that an electric current flows in the wire
wound around the compass. The relative motion of the elec-
tromagnet b and the coil a, one within the other, causes an
electromotive force to be induced or generated in the coil a,
and an electric current results. If the two coils remain
stationary, one within the other, and the exciting current of
the solenoid is steady, the needle is not affected; but, when-
ever either coil is moved with reference to the other, the
needle will be deflected — one way for relative movement in
one direction and the other way for movement in the other
direction.

Furthermore, if the coil b is placed inside of coil a and the
current in coil b is rapidly altered in strength, as for instance,

Fig. 12

by opening or closing the circuit containing the coil b and
battery /, a current will be induced in coil a. The current
induced in coil a will flow in one direction when the circuit
of b is closed or the strength of the current in b is rapidly
increased, and in the opposite direction in coil a when the
circuit of b is opened or the strength of the current in b is
rapidly decreased. The closing and opening of the circuit
of 6, thereby inducing a current in a first in one direction and
then in the opposite direction, is the action that takes place

222—9

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20 ELECTRIC IGNITION § 6

in practically all automobile induction coils. However, to
increase the strength of the induced current in the coil a,
the coil 6 is invariably filled with soft-iron wire. Since the
iron wire is more permeable than air to magnetic lines of
force, more of them are produced both inside and outside of
the solenoid b when it is filled with iron than when it is filled
with air. Although the lines of force outside the coil are
always equal in number to those inside, they are farther
apart and the outside magnetic field is therefore less intense.

The effect of inserting a magnetized piece of iron, as for
instance, a permanent bar magnet, in a coil or withdrawing
it from the coil, is the same as would be produced by putting
one coil, through which a current is flowing, within another
coil or by withdrawing it. In each case a current is induced
in the outer coil.

If the number of lines of force through the coil a, Fig. 12,
is unchanging, as when the solenoid or the magnet is held
stationary with reference to the coil, no effect is shown by
the needle; but every time a change occurs in the number of
lines of force enclosed by the coil a, an electromotive force is
induced in it, and the resulting current causes the needle to
deflect.

IGNITION APPAKATUS

BATTERIKS

DEFINITIONS AM> CLASSIFICATION

41. When a number of cells are connected together,
as is customary in practice, they form an electric battery.
In commercial usage, however, the term battery is indis-
criminately applied both to a group of electrically connected
cells and to a single cell; a single cell is also known as a
battery cell.

42. In electrical diagrams, cells are represented as in
Fig. 13; M and N each represent a single cell, a and c being

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§ 6 ELECTRIC IGNITION 21

the positive electrodes and b and d the negative electrodes.
The two cells joined together as shown constitute a battery,
a and d representing the terminals of the battery, as well as
the positive electrode of M and the negative electrode of N,
respectively. The closed loop connecting a and d is a circuit.
The arrows indicate the direction in which the current flows.

43, The electric batteries used for ignition purposes are
of two distinct classes: primary batteries and secondary, or
storage, batteries. Secondary batteries are also known as
accumulators. The priman'^ battery will deliver electric
current as soon as its parts are assembled, but with the
storage battery, electricity
from some separate source
of supply must be stored
in it before it becomes
electrically active. The
primary batteries used on
automobiles are known as
dry batteries, because they P'o- 13

have no free body of liquid to flow and splash. Primary
batteries having a free body of liquid are called wet batteries,
the principles of which have been described in connection
with the cell shown in Fig. 2.

POLARIZATION AND DEPOLARIZATION

44, If the circuit shown in Fig. 8 is left closed for a
considerable time and the tack then pulled off, it will be found
that the electromagnet will not hold the tack again, although
the electric circuit has remained closed all the time; or, if
the apparatus is left standing with the circuit closed and the
tack suspended from the nail, the tack may become loose
and fall off of its own accord, generally after a long time.
That this dropping may occur, the tack shotdd be of about as
great a weight as the magnet will support when the electric
circuit is first closed. The failure of the nail to hold the
tack after the current has been flowing continuously for some

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22 ELECTRIC IGNITION § 6

time is due to a decrease in the amount of current flowing.
The chemical action in the cell or battery required to produce
t^ie electric current liberates hydrogen gas, which collects
as small bubbles on the carbon and prevents intimate contact
between the carbon and the electrolyte, and the cell is then
said to be polarized. This polarization reduces the
amount of chemical action, and consequently less current is
produced. If the surface of the carbon is made very large
in proportion to that of the zinc, the polarization does not
occur so rapidly, nor is it so decided as in a cell of the pro-
portions shown in Fig. 2, which is about 8 inches high.

If the electric circuit is broken, and the apparatus is left
standing on open circuit for a few minutes and then closed,
the current will again be sufficient to magnetize the nail so
as to support the tack. The battery thus recuperates by
depolarizing itself while resting. Besides the objection to
the use of a liquid, such a battery is not suitable for auto-
mobile ignition because of polarization.

45. Depolarizatiou is accomplished chemically by
surrounding the carbon plate with some substance with which
the free hydrogen can combine. There are many kinds of
depolarizing primary cells, some with solid and some with
liquid depolarizers.

PRIMARY BATTERIES

46, Wet Cells. — Although serviceable for ignition
purposes with stationary gas and gasoline engines, battery
cells of the wet type are not suitable for use on automobiles,
because they are usually easily broken. Besides, they are
too bulky, and the motion of the car causes the liquid elec-
trolyte to be thrown out of the jar. For use on portable
traction gasoline-engine outfits, the manufacturers of the
Edison-Lalande wet cell make a steel, porcelain -enameled
jar that can be made liquid tight, but the number of cells
necessary to obtain the required voltage for automobile-
engine ignition, and also the large space required, precludes
the feasibility of using them for that purpose, even though

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§6

ELECTRIC IGNITION

such cells have a much longer life than the dry type of cell
commonly employed.

47. Dry Cells. — Fig. 14 shows a section of a dry cell
such as is used for automobile ignition. The carbon rod c
is placed in the center, and the zinc forms the enclosing cup,
or a can a. Next to the can is a lining p of absorbent paper
that is completely saturated with a liquid electrolyte con-
sisting of sal ammoniac and zinc chloride dissolved in water,
and next to the paper is a thin layer d of white paste.* The
space between the carbon rod and the lining of the cup is
filled, except at the top, with the depolar-
izer m, which is a mixture of powdered
carbon or coke and manganese dioxide.
The cell is sealed water-tight with pitch
or some similar substance, which fills the
space above the depolarizer, and is per-
manently wrapped, except over the top,
with pasteboard and paper, to prevent
metallic contact with other cells in a bat-
tery.

The positive terminal is at the center
of the top, and the negative terminal is a
binding screw attached to the top edge
of the zinc cup. The cell generally used
for automobile ignition is 2^ inches in
diameter and 6 inches long. Other dry
cells similar in general appearance to the
one just described, but differing in some
of the materials employed, are also extensively used for
ignition.

Dry cells of the size just mentioned usually have, when
new and in good condition, an internal resistance of from .1
to .7 ohm and an electromotive force of 1.3 to 1.6 volts.
As a rule, the best dry cells will not remain in good condition
more than 2 or 3 years ; and good results should not be expected
from cells that have been kept in stock for only 1 year.

Pig. 14

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24 ELECTRIC IGNITION § 6

BATTERY CONNECTIONS

48, If it is desired to have more current than one celj
will give, this increased current can be obtained by connect-
ing cells together. Evidently, two cells can be connected
in two ways: Either the positive ( + ), or carbon-plate,
terminal of one cell can be connected to the negative ( — ),
or zinc-plate, terminal of the other (carbon to zinc), as in
Fig. 15, which shows a series connection; or similar terminals
can be connected together, as in Fig. 16, which shows a
multiple, or parallel, connection. Both of these arrange-
ments will give more current than will a single cell under
any condition.

If the external resistance of the circuit is greater than the
internal resistance of one cell of a battery made up of the

Fio. 15 Fig. 16

same size and kind of cells, which is usually the case in
automobile service, then series connection will give more
current than parallel connection. In Fig. 15 and succeeding
diagrams of wiring connections, the positive, or carbon-
plate, terminal is located at the center of each cell, the nega-
tive, or zinc-plate terminal being placed at the edge of each
cell, as is customary in actual practice.

49. Sorlos-Battery Connections. — If two or

more cells are connected in series, as in Fig. 15, the positive
terminal of one and the negative terminal of the other become
the terminals of the battery. The voltage of the battery is
measured between the battery terminals. When the circuit
is open, as shown, the voltage of the two-cell series-connected
battery is twice that of one cell, provided the cells are alike
or have the same voltage. In any case, the battery voltage
of series-connected cells on open circuit is equal to the sum
of the voltages of the two cells. If each cell gives 1.5 volts,

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§ 6 ELECTRIC IGNITION 25

then the battery of two series-connected cells will give
2 X 1.5 = 3 volts. If four cells are put in series, as in Fig. 17,
the voltage will be 4X1.5 = 6 volts. Six cells in series will
give 6X1.5 = 9 volts.

In series-connected cells, the internal resistance of the
battery is increased by the addition of cells. Thus, the
resistance of a two-cell series battery is twice that of a single
cell, provided the cells are alike and in the same condition;
of a four-cell battery, four times that of a single cell; and
of a six-cell battery, six times that of one cell.

50. The total resistance of a circuit containing primar}'
cells is equal to the internal resistance of the battery plus
the resistance of the external circuit. The resistance of a
given external circuit remains approximately constant,
while the internal resistance varies with the number of cells

Fig. 17

constituting the battery. Hence, the total resistance does
not vary in direct proportion to the .number of cells in the
battery. For instance, if the external resistance is 5 ohms
and the battery consists of six cells, each having an internal
resistance of .4 ohm, the internal resistance will be 6X.4
= 2.4 ohms, and the total resistance of the circuit will be
2.4 + 5 = 7.4 ohms. If two cells are added, the internal
resistance will be 3.2 ohms and the total resistance 8.2 ohms.
It will thus be seen that the total resistance of the circuit
does not vary proportionally with the niunber of cells; in
other words, the total resistance increases less rapidly than
the number of cells. Now, it has been shown that the
electromotive force of a battery of similar cells is proportional
to the number of cells; that is, if the voltage of six cells is
6X1.3 = 7.-8, the voltage of eight similar cells will be 8X1.3
= 10.4.

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26 ELECTRIC IGNITION § 6

The current flowing in a circuit containing a battery and
an external resistance is equal to the voltage of the battery
measured on open circuit divided by the total resistance of
the circuit.

Example 1. — If there are six cells, each having an open -circuit
voltage of 1.3 and an internal resistance of .4 ohm, what current will
flow through an external circuit of 5, ohms?

Solution. — The voltage of the battery is 6X1.3 = 7.8; the internal
resistance, 6X.4 = 2.4 ohms; and the total resistance of the circuit,
2.4 + 5 = 7.4 ohms. Therefore, the current through the entire circuit
is 7.8^7.4 = 1.05 amperes. Ans.

Example 2. — If there are eight cells, each having an open -circuit
electromotive force of 1.3 volts and an internal resistance of .4 ohm,
connected to an external circuit of 5 ohms, what current will flow
through the circuit?

Solution. — The voltage of the battery is 8X13 = 10.4 and the
internal resistance, 8X.4 = 3.2 ohms. Therefore, the total resistance
of the circuit is 5 + 3.2 = 8.2 ohms, and the current through the circuit
is 10.4-^8.2 = 1.27 amperes. Ans. ,

51. Be versed Connections in Series Battery. —

If one of the cells in a series battery is reversed, as shown

Fig. 18

in Fig. 18, the voltage on open circuit will be reduced to the
same extent as if two cells had been removed from the prop-
erly connected battery of the same number of cells. The
pressure of the reversed cell counteracts the pressure of one
of the properly connected cells. Primary cells in a series
battery are not injured by the reversal of one or more of them.

52. Multiple or Parallel Battery Connections. — If

two or more cells are connected in parallel, carbon to carbon
and zinc to zinc, the carbon side will be the positive terminal

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§ 6 ELECTRIC IGNITION 27

and the zinc side the negative terminal, as shown in Fig. 19.
The voltage, or pressure, remains the same as for one cell.
The internal resistance of the battery is reduced below
that of one cell, because there is a greater sectional area of
battery materials for the current to pass through. There-

Fio. 19

fore, the total resistance of the complete circuit, external
plus internal, is reduced by increasing the number of parallel-
connected cells. As the pressure remains unchanged, the
ratio of the pressure to the total resistance is increased, and
this means an increase of current. The internal resistance
of two similar cells in parallel is half that of one cell; of
four similar cells in parallel, one-fourth that of one cell;
and of six similar cells, one-sixth that of one cell. All
the cells of a parallel-connected battery should be of the same
make, or at least made of the same materials, and should
have the same voltage. It is best to have all of them just
alike. If cells giving different pressures are used, the action
will be similar to that described in the next article.

=5^:

Fig. 20

53. Keversed Connections in Parallel Battery. — If

one of the cells in a parallel-connected battery is reversed,
as shown at a. Fig. 20, the current will flow, as indicated by
the arrows, until the cells properly connected in parallel
are exhausted. The reversed cell corresponds in a way to
a closed external circuit, which, with dry cells, is of small
or low, resistance. Hence, the real external circuit will
receive practically no current.

Example. — If a battery consisting of two cells connected in parallel,
each cell having a voltage on open circuit of 1.3 and an internal

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28 ELECTRIC IGNITION § 6

resistance of .4 ohm, is connected to an external circuit of 5 ohms,
what will be the current in the external circuit?

Solution. — The voltage of the battery is 1.3; the internal resistance,
.4 -^ 2 = .2 ohm; and the total resistance of the circuit, .2 + 6 = 5.2 ohms.
The current in the external circuit is therefore 1.3 -J- 5.2 = .025 ampere.

Ans.

54. Parallel-Series Battery Connections. — If two

series batteries of the same number of like cells are

connected in parallel, as
in Fig. 21, the pressure
will be the same as that
of one series. Each series
of cells may be considered
as a unit and may be
I dealt with as a single cell
having a pressure and a
Fig. 21 resistance equal to that of

the series. Thus, if the series consists of four cells having a
pressure of 1 .5 volts each, the pressure of the unit will be 4 X 1.5
= 6 volts, and the internal resistance of the unit will be four '
times that of one cell. The internal resistance of a battery of
two series sets, each set of the same number of cells, is one-half
that of one set, or unit. For three series of four cells each,
the internal resistance is one-third that of one set having
four cells in series. When there are as many series as therfe
are cells in each series, the internal resistance of the battery
is the same as that of one cell.

Each series of cells forming a unit should have the same
number of cells; otherwise, the higher pressure of the series
having the greater number of cells will force current back
through the series having the smaller number and exhaust
the cells in the larger series. A reversed cell in a parallel-
series battery has much the same bad effect as a reversed
cell in a single parallel arrangement of cells, as explained
in the preceding article.

Example. — A battery consists of eight cells connected in two
parallel rows of four cells in series in each row. Each cell has an

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§6 ELECTRIC IGNITION 29

electromotive force of 1.3 volts and an internal resistance of .4 ohm.
What current will flow from this battery through an external circuit
of 5 ohms?

Solution. — The voltage of one row of four cells in series is 4X 1.3
= 5.2. Putting cells in parallel does not increase the voltage; hence,
the voltage of two parallel rows of cells is the same as that of one
row, and in this case the voltage of the battery is 5.2. The internal
resistance of one row is .4 X .4 = 1.6 ohms; but two rows in parallel will
have one-half the resistance of one cell. Hence, the internal resistance
of the battery is 1.6 -5-2 =.8 ohm. The total resistance, therefore, is
.84-5 = 5.8 ohms, and the current in the external circuit is
5.2 -7- 5.8 = .896, or .9, ampere. Ans.

55. Increasing the number of good cells in an ignition
circuit will increase the current in the circuit, provided, of
course, that the cells are properly connected. The total
electromotive force is increased as the number of cells in
series is increased ; or, the internal resistance of the battery is
decreased as the number of sets of cells in parallel is increased.
In both cases, however, the resistance of the external circuit
remains unchanged. Hence, the current is increased in the first
case because the electromotive force applied to the circuit
increases faster than the internal resistance of the battery

Fig. 22

increases the total resistance of the circuit. In the
second case, the electromotive force and external resistance
remain constant, but the internal resistance, and hence the
total resistance of the circuit, is decreased. See Arts. 49,
50, and 52.

56. Battery-SM^itcli Connections. — The switch for
coimecting two series batteries to an external circuit shotdd

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30 ELECTRIC IGNITION § 6

be made and located so as to break the connections in such
a manner, when opened, as to make it impossible for any-
current to flow'between the different sets of cells. Exhaustion
of the battery when not in use is thus prevented. Fig. 22
shows the correct method of connecting a switch to a battery
consisting of two series of cells. The wires R lead to the
external circuit. When the switch is closed in the position
shown, only series A is brought into operation, and when the
switch is moved to the dotted position, only series B is put
into circuit and A becomes idle. If the switch is placed
in mid-position so that the lever touches both contacts, all
the cells are in use, A and B working in parallel.

Fio. 23

The arrangement shown in Fig. 23 is not a good way of
making the connections, even if the whole battery is always
to be cut in when current is wanted. If, in a battery con-
nected in the manner shown, series A happens to be in
better condition than series By which may be taken to mean
that its pressure is higher, current will flow in the direction
indicated by the arrows when the switch is open. This flow
will continue until the pressure of series A has fallen to the
same as that of series B.

SECONDARY, OR STORAGE, BATTERIES

57. The activity of a storage battery, accumulator,
or secondary battery depends on internal chemical
action produced by passing an electric current through it
from some external source of supply. This operation is

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ELECTRIC IGNITION

called charging the battery. After the battery is charged,
it will discharge through a closed circuit nearly the same
quantity of electricity as was used to bring about the original
chemical action. The positive terminal of a storage battery
is the one by which the charging current enters and the
discharging current leaves. The majority of storage batteries
used for electric ignition may be called lead accumulators,
since lead and its oxides enter most prominently into their
construction. In some of the other types of storage batteries

Pig. 24

less used, but gaining in prominence, iron and nickel are
used instead of lead.

58. The plates, or i^rtds, of a lead accumulator are
made either of lead, or lead alloy, with pockets, grooves,
or recesses for holding the active material. They also have
he3Lvy lugs, or shoulders, to which the terminals are attached.
In Fig. 24 (a) is shown a single plate, the minute grooves

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ELECTRIC IGNITION

§6

of which are filled with lead oxide, and in (b) is shown a com-
plete cell with the plates assembled in a glass vessel. The
lugs on alternate plates are connected together by a strip of
the same material as is used for the metal of the plates, an
extension of which fonns one of the terminals of the cells.
The remaining plates are fastened together and are provided
with a teniiinal in a similar manner. The terminal strips
are attached to the plate by melting, or burning, the parts
together where they are in contact. The vessel is filled

with an electrolyte of
dilute sulphuric acid, so
as to cover the plates
completely.

59. The containing
vessel of the battery
may be either of glass
or of rubber, and where
lightness and compact-
ness are desirable, as in
batteries for automobile
ignition, this vessel is
sometimes made of or
lined with lead and may
be utilized to serve as
one of the plates. In
any case, the plates
are arranged quite close to each other. Strips or other
forms of insulating material are placed between the plates
to prevent them from coming into metallic (electric) contact.
Some of the insulating materials thus used as plate separators
are glass, hard rubber, and wood.

60, There are two general types, or classes, of lead accu-
mulators, named from the inventors of the methods of making
the plates. These are the Plants type, in which the plates
are formed by electrochemical action that causes a deposit
of an oxide of lead on the plates, and the Faure tyi>e, in
which the oxide is made into the form of paste and put into

Fio. 25

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§ 6 ELECTRIC IGNITION 33

suitable grooves, or recesses, in the sides of the plates. Lead
oxide is the active material in each case.

61. ' Fig. 25 (a) shows a sectional view of a small storage
battery made for automobile-engine ignition purposes. At a
is shown the side of the positive plate supported on hard-
rubber insulators 6, and in (6) is shown an enlarged end view
of the same plate before forming. When the plate has been
electrochemically formed, all the grooves are filled with
oxide of lead. The other parts of the cell in (a) are as follows:
At c is shown the positive terminal and at d the negative
terminal carrying a binding post e; at /, the electrolyte con-
tained in a hard -lead jar g; at fc, a hardwood case; and
at i, a hard-rubber cover fitting tightly in the lead case;
at y, a sealing compound filling the space between the lead
jar and the hardwood case and also the space over the cover;
and at k, a hard-rubber tube that contains a glass valve /
and is closed by a rubber stopper m.

The cell is so' effectually closed that it can leak but little,
even if turned upside down. The solution used in a storage
cell can be made semidry either by using an absorbent or
by introducing some substance, such as a silicate of soda,
to form a jelly with the acid. There is, however, a tendency
for a semidry storage battery to dry out completely and thus
become useless. This is especially true in a warm locality.

62. The voltage of a storage cell varies from about 2.5
when fully charged to about 1.7 when completely discharged.
The pressure falls rapidly, to the extent of about tV volt,
when the battery first begins to discharge after being fully
charged. When the voltage has dropped to about 1.7 per
cell, the .battery should be recharged, because it retains only
a comparatively small amount of electric energy at this
pressure, and the voltage drops rapidly during discharge after
getting this low. The life of the battery is shortened by
discharging below 1.7 volts per cell.

Storage batteries for ignition purposes are generally made
up of either three cells in series, giving an average voltage

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34 ELECTRIC IGNITION § 6

during discharge of about six, or two cells in series, with an
average discharge pressure of about 4 volts. These two
pressures are adapted to meet the requirements in operating
induction coils.

The electric resistance of a storage cell such as is used for
automobile ignition is generally higher than that of a storage
cell used for the propulsion of automobiles and other vehicles,
but it is far lower than that of a dry cell as ordinarily con-
structed. If a storage cell is short-circuited, the flow of
current will be excessive and injurious to the battery. The
maximum rate at which a storage cell or battery should be
charged and discharged is generally indicated on instructions
that accompany the battery.

63. The capacity of a storage battery is generally stated
in ampere-hours. If a battery discharges continuously at
the rate of 2 amperes for 30 hours, its capacity is 2x30
= 60 ampere-hours. Such a battery will deliver 4 amperes
for 15 hours, or 1 ampere for 60 hours. The battery will
deliver a slightly greater number of ampere-hours when
discharged slowly, as in ignition use, than when the discharge
is rapid.

64. €liar§rln§r of Storagre Batteries. — A direct cur-
rent must always be used for charging the storage battery.
In case only an alternating current is available, an alternating-
current rectifier of some kind must be used for changing it
into direct current.

When charging a battery from any source, especially if
there is any doubt as to the direction of flow of the current,
a test should be made to make sure that the positive plates
are connected to the positive terminal of the charging circuit.
A simple way to make this test is to attach two wires to the
source of current supply and then dip their free ends into
water -made slightly impure by the addition of a salt or an
acid. Sulphuric acid, sal ammoniac, or common salt will
sen^e the purpose. The ends of the wires should be kept
well apart at first and then gradually brought nearer together,

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§ 6 ELECTRIC IGNITION 35

but they should be allowed to touch each other until bubbles
of gas are given off at one of the wire ends. Bubbles may be
given off at both ends, but they will come much more rapidly
from the negative end than from the positive end. The
immersed wire end that gives off most bubbles is the one to
be connected to the negative terminal of the storage battery ;
the other wire should go to the positive terminal of the storage
battery. The positive terminal of a storage battery for
automobile ignition is generally indicated by the (-I-) sign,
and sometimes it is painted red. The polarity of the storage-
battery terminals may also be determined in the foregoing
manner.

If the source of current supply is of considerable capacity,
so that a short circuit would be injurious, the vessel contain-
ing the water into which the wire ends are dipped should
be of glass or some other insulating material so as to avoid
short circuiting, and the supply circuit should contain a fuse
having, preferably, a capacity of 5 amperes or less. If the
voltage is high, resistance should be put in series with the
submerged wires, so as to prevent injury in case they get
too near together.

There are several other simple methods of determining
which is the positive side of the source of the current supply.
Among these are the turning red or blue of a solution by the
passage of a current through the liqtiid. Small and convenient
sealed-glass-tube instruments depending on this action are in
use. The positive and negative sides are generally indicated
on the instrument. Some electric-pressure measuring instru-
ments can be used for the same purpose. When such instru-
ments are properly connected across the circuit, the voltage
of the circuit will be indicated; when incorrectly connected
across the circuit either no indication will be given, or a
deflection in the wrong direction will occur.

65. The battery should be charged not more rapidly
than at a rate determined by its capacity in ampere-hours,
the charging current, in amperes, being equal, for an ordinary
battery, to the ampere-hour capacity divided by 8. Thus, a

222—10

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ELECTRIC IGNITION

§6

60-ampere-hour battery should be charged at 7.5 amperes or
an 80-ampere-hour battery at 10 amperes. Another, and
perhaps better, rule is to charge at a rate not exceeding one-

I II

^ M H ! I

I'l

^i|ir+

(e)
Fig. 26

sixth the ampere-hour capacity, and then maintain this rate
by gradually cutting out resistance until the voltage reaches
2.4 or 2.5 per cell, when the cells begin to gas. The charging
current should then be cut down to one-twentieth the ampere-

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§ 6 ELECTRIC IGNITION 37

hour capacity until the cells again gas freely, indicating a
full charge.

If the battery is charged from a direct-current, incandescent-
light circtiit, there must be used in series with the battery a
resistance sufficient to absorb the greater portion of the volt-
age of the charging circuit. For this purpose, a bank of lamps
is generally employed. As the internal resistance of the
battery is so small as to be almost negligible, it follows
that a 100-volt lamp must be used for- each 100 volts
tension of the charging current, or a 110-volt lamp for a
110- volt current.

66. Wiring connections for charging storage batteries
from direct-current lighting and power circuits are shown
diagrammatically in Fig. 26. Connections to a 110-volt
lighting circuit are shown in (a). A double-pole switch a,
with fuses 6, is connected between the mains and the battery,
as shown. In series with the battery c is a number of lamps,
by means of which the charging current is limited to the
proper amount. It is advisable to connect an ammeter d in
circtiit, though this is not absolutely necessary.

The number of lamps required depends on the line voltage
and on the charging rate of the cells. If the line pressure
is 100 to 120 volts and only three or four cells are to be
charged with a current of 5 amperes, then five 32-candle-
power lamps requiring 1 ampere each, connected in multiple,
as shown in (a), will be sufficient. If 16-candlepower lamps
reqtiiring i ampere each are used, it will be necessary to
connect ten in parallel. With a 220-volt circuit, there will be
required twice as many lamps as with the 110-volt circuit, the
second set of lamps being placed in series with the first. If
the line pressure is 500 volts, it will be necessary to connect
twenty-five 32-candlepower lamps in five rows of five lamps
in series in each row, as shown in (6), or fifty 16-candlepower
lamps in ten rows, five lamps in series in each row. In case it
is convenient to charge at a lower rate, fewer rows of lamps
will be needed, but the time for charging will be proportion-
ately increased.

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38 ELECTRIC IGNITION § 6

To charge a low- voltage battery, such as an ignition
storage battery, from a 500-volt, direct-current circuit is a
very inefficient method. The high voltage makes it some-
what dangerous and requires that very good insulation be
used throughout the circuit.

67. Lamps form a convenient resistance, as they are
easily obtained, but an adjustable rheostat is frequently used,
as shown at r, Fig. 26 (c). The amount of resistance required
in the rheostat may be calculated by subtracting the approx-
imate voltage at which the storage battery should be charged
from the charging line of voltage, and then dividing this
difference by the desired charging current.

Example. — A 6- volt ignition storage battery is to be charged
from a 110- volt circuit. How much resistance should be connected
in series with it, if the charging current is to be 4 amperes?

Solution. — The difference between 110 and 6 is 104 volts. There-
fore, 104 -^ 4 = 26 ohms. Ans.

This resistance should be adjustable, so that some of it can be cut
out as the voltage of the cells increases, and it must be made of wire
large enough to carry at least 4 amp)eres without overheating.

Charging with resistance in series is at best a makeshift,
because it involves a large loss of energy; but in the case of
small, portable batteries, this waste is not a very serious
matter, especially as the use of the series resistance gives
the most convenient and simple means of charging from
existing circuits.

68. Becliar^n^ of Storage Batteries When Not
In Use. — To keep a storage battery in good condition,
it should be charged at least once a month, whether used
or not, and it should preferably be kept in a cool place. Of
course, if its full capacity has not been used, not so many
ampere-hours will be reqtiired to recharge it. If the battery
is not to be used, recharging it once very 2 months may be
sufficient, provided the battery is kept in a cold place. It
should not, however, be allowed to freeze.

An ordinary ignition storage battery should not be permitted
to stand without any solution in it, because in such a case

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§ 6 ELECTRIC IGNITION 39

the wooden separating pieces between the plates will rot
and the battery will have to be taken to pieces in order to
replace them when it is to be used again.

69. liayln^ Up of Storage Battery. — If the battery
must be laid away, say for 6 months or longer, without
recharging, proceed as follows: After thoroughly charging
the battery, remove the electrolyte into convenient clean
bottles or other non-metallic receptacles that can be closed
tightly, so as to preserve it for future use. Then refill the
battery with fresh, pure water, allow it to stand for 12 or
15 hours, and pour off the water. The plates are then in
a condition to stand indefinitely. However, if the plates
are held apart by wooden separators, these should be removed
before drawing off the water; otherwise, they will rot. If
the separators are in good condition, they may be used again,
provided they are kept submerged in water. Generally,
it will be foimd better to throw them away and use new
separators when the battery is to be used again.

Most ignition batteries are covered with a seaUng com-
pound, and to put such a battery out of use in the manner
just described, it will be necessary to remove this compound,
as well as the plates and their wooden separators, from the
case. The compound and plates may be removed, usually
together, by running a heated knife between the case and the
compound. Before removing the compound and plates,
it may be possible to find out from the maker of the battery
whether the separators are made of wood or of some other
material. If they are made of hard rubber or glass, their
removal is unnecessary. Any sediment in the battery
should be thoroughly washed out or otherwise removed
when the battery is put out of use. Rather than lay an
ignition storage battery away with no solution covering the
plates, it is usually preferable to give the battery a freshening
charge every month, or at least every 2 months.

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40 ELECTRIC IGNITION § 6

AL.TERNATING-CURRBNT CONVERSION FOR BATTERY
CHARGING

70. To make use of alternating current in charging
storage batteries, it must, as has already been mentioned,
be converted into direct current. Two distinct kinds of
apparatus are used for obtaining direct cturent from an
alternating-current circuit. One is of the nature of a com-
bined electric motor and electric generator, called a motor-
generator; the other, known as a mercury^apor converter^
or rectifier, has no moving parts, except such as are moved
for starting it.

71. Motor-Generators. — By connecting an alter-
nating-current electric motor to a direct-current electric
generator, so as to drive the latter mechanically, a direct
current for storage-battery charging can be obtained from
the generator. The electric pressure of the direct current
must, of course, be suitable, and an electric resistance, vari-
able at the will of the operator, is usually necessary in order
to regulate the amount of current flowing through the storage
battery. Instead of using two separate machines, however,
it is customary to employ a motor-generator, which is a
compact machine that appears externally much like an ordi-
nary electric generator, but is really two machines in com-
pact form on the same base.

One common type of motor-generator has two armatures
on the same shaft, one being wound for alternating current
and the other for direct current. The motor armature has a
slip ring and collector brushes, through which the alternating
current is led to it, while the generator armature has a seg-
mental commutator and brushes, through which the direct
current generated in the armature is transmitted to the
circuit containing the storage battery to be charged.

72. Rectifiers. — The operation of a mercury-vapor
rectifying? apparatus for alternating current depends
on the fact that the vapor of mercury — a liquid metal much
used in thermometers — allows current to flow through it in

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§ 6 ELECTRIC IGNITION 41

one direction under certain conditions, but opposes its flow
in the opposite direction. Except in some designs, after the
apparatus is started, none of its parts move.

73. With some forms of alternating-current rectifiers
on the market, dependence is placed on chemical action for
rectifying the current; but as now made and used, they
appear to be inefficient and expensive to operate when
compared with mercury-vapor apparatus.

SPARK COLLS

INDUCTANCE, OR KICK, COILS

74, If a short piece of wire is connected to one of the
terminals of a dry battery, and the free end of the wire is
struck against the other terminal, a small spark will generally
appear as the contact between the wire and terminal is
broken; that is, at the instant the wire is drawn away from
the terminal. If a wire several feet long, say 15 feet of No. 28,
B. & S. (.0126 inch in diameter) copper insulated magnet
wire, not coiled, is used in the same manner, the spark will
be smaller, assuming that the short wire is of the same size
as, or at least not much thinner than, the long one. In order
to make the case simple, it will be assumed that both wires
are of the same thickness. The smaller spark with the
longer wire is due to the smaller amount of current that
flows through it on account of its greater resistance.

If the longer insulated wire is now wound around a wooden
lead pencil into as short a coil as possible, with the turns
piled on top of each other, so that there are a hundred turns
or more, a more decided spark will be produced, the longer
spark being due to coiling of the wire. The spark is stronger
when the circuit is broken quickly than when the separation
of the contact points is slow.

The current in the coil decreases, of course, from its maxi-
mum strength to zero when the connection is broken and the

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42 ELECTRIC IGNITION § 6

circuit opened. The decreasing current in each turn of the
coil acts inductively on the current in the other turns in such
a manner as to resist sudden decrease. Consequently, the
current continues for a longer time across the space between
the separated contact points, and when the points are sepa-
rated quickly, it also continues across a longer space or a
wider gap. The wooden lead pencil has no effect on the spark.
This action of the coil is called self-induction. Self-
induction tends to prevent a rapid change in the strength of
an electric current.

75. By substituting a piece of soft iron for the lead
pencil, the spark will be made still stronger. This is due to

the fact that the iron,
which is a magnetic sub-
stance, allows the same
current in the same coil
to produce more lines of

force through it. The
iron resists any change in
its magnetism; hence, the
decrease of magnetism in
the iron core of the coil as
^*°* ^ the current decreases tends

to prevent a rapid decrease of current.

A change in the current in the coil induces in the iron core
electric currents that reduce the rapidity with which the*
magnetism of the core diminishes, thereby reducing the
rapidity with which the current in the coil decreases. Smaller
currents are induced in a core made of a bundle of small iron
wires than in a core that is solid. This is due to the resistance
offered by the dirt, grease, and rust on the surface of the
wires. Hence, a wire core causes less decrease in the rapidity
with which the current in the coil decreases, and consequently,
a greater spark is produced by a given coil with an iron-wire
core than one with a solid-iron core.

The reduction of the rate of increase of current when the
circuit is closed is of no importance in connection with

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§ 6 ELECTRIC IGNITION 43

ignition by the contact method, with which system of ignition
inductance coils are used.

76. In technical phraseology, a coil of insulated non-
magnetic wire, with a soft-iron core made up as just described
is known as an Inductance coll, but in connection with
electric ignition it is variously designated as a make-and-break
coil, a primary spark coil, and a kick coil. The term spark
coil is also applied to it as well as to other types of coils used
for ignition purposes. When used in conjunction with a
battery that gives enough current, a kick coil of sufficient
inductive strength will produce a spark hot enough to ignite
a combustible gaseous mixture. Such a coil, suitably
mounted, is shown in Fig. 27. The two screws with nurled
nuts are the terminals of the coil.

INDUCTION COIIiS

77, Suppose that to a kick coil like the one shown in
Fig. 27 is added another coil of insulated wire, wound around
the outside of the coil so that the two coils are concentric,
the ends of the wire of the outer coil being connected together
electrically, metal to metal. Then by connecting the wires
of a battery to the terminals of the kick coil an electric current
will be induced in and flow through the outer coil during the
time that the battery current is gaining its full strength.
As soon as the battery current gains its full strength, the
. current in the outer coil will cease, and there will be no current
in it while the battery current continues to flow steadily;
but if the battery current is interrupted, current will again
be induced in the outer coil during the time that the battery
current is dropping to zero value. The current is induced
in the outer coil only during the time that the current is
changing in strength in the inner coil. Any change in the
strength of the current in the inner coil induces a current
in the outer coil. The strength of the induced current is
proportional to the rate, or rapidity, of change of current in
the inner coil.

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44 ELECTRIC IGNITION § 6

The coil through which the battery current flows is called
the primary coll; and that in which current is induced,
the secondary coll. The current in the primary coil is
called the primary current, and the induced current in
the secondary coil, the secondary current.

While the primary current is increasing, the induced second-
ary current flows in a direction opposite to that of the primary
current; and while the primary current is decreasing, the
secondary current flows in the same direction as the primary
current. Thus, as the primary circuit is closed and opened,
the secondary current flows first in one direction and then
in the other.

78. If the ends of the wires of the secondary coil are
separated and left apart, there will be a difference of electric
pressure induced between them when the current in the
primary coil is either increasing or decreasing. The intensity
of this pressure is proportional to the number of turns in the
secondary coil, or approximately so. It is also proportional,
in a measure, to the number of turns in the primary coil
and to the rate of change of the primary current. With a
large primary current, the rate of change is more rapid than
with a small current when the circuit is closed or opened.

When the secondary coil has a very great number of turns,
a battery of even moderate size will supply sufficient current
to induce a pressure high enough to cause a spark to jump
across the air gap between the ends of the wire of the secondary
coil when they are a short distance apart. On account of
the great difference between the pressure used to send current
through the primary coil and that induced in the secondary
coil, the primary is also called the low-tension coll, and
the secondary, the bl^b-tenslon coll.

79. The primary current can be stopped more abruptly
by connecting an electric condenser to opposite sides of the
point where the primary circuit is broken. The more abrupt
cessation corresponds to a more rapid rate of change in the
strength of the primary current, and consequently a higher

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§ 6 ELECTRIC IGNITION 45

tension is induced in the secondary coil. There is also less
tendency to bum, or fuse, the contact points in the primary
circuit Vhen a condenser is attached.

80. An electric condenser, such as is used for
ignition on automobiles, is made up of a number of sheets
of tin-foil and sheets of some insulating material, such as
paraffined paper, laid together alternately, so that adjacent
sheets of the tin-foil are instdated from each other by the
paper. In Fig. 28 the lines a and h represent the edges of
the tin-foil sheets, and the heavy lines i, the edges of the
sheets of insulating material. All the alternate sheets of
tin-foil a are connected to-
gether by a conductor, and
all the remaining tin-foil
sheets 6, by another con-
ductor. These two conduc-
tors are generally known as
the sides of the condenser. ^
The sheets may be curved as
well as flat.

81. A transformer, or
non-vibrator induction- *
coll — Q, coil without any pro- ^*° ^

vision in itself for opening and closing the primary circuit — ^is
frequently used in connection with a mechanically driven
electric generator to produce a jump spark in a high-tension
ignition system. The generator is provided with means of
opening and closing the circuit in such a case.

Fig. 29 shows a non-vibrator coil, or transformer, and a
condenser connected up with a battery and a switch for
closing and breaking the primary circuit. The primary
winding or coil a is surrounded by the secondary coil 6, and
within it is the magnetic core c made up of a bundle of soft-
iron wires. The battery d is in circuit with the primary coil,
and the condenser / is connected to the primary circuit on
opposite sides of the switch e.

T«'

3;=

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ELECTRIC IGNITION

§6

When the arm h of the switch rotates about g, the contact
point on it touches the terminal to which the end i of the
primary wire is attached and closes the primary circtiit.
Current immediately begins to flow through the primary
coil, and the rate of current increase may be rapid enough to
induce sufficient tension between the terminals of the second-
ary coil to make a spark jump between the ends of the wire
at ;*. The condenser has no appreciable effect when the
circuit is closed and the current increasing, or when the cur-
rent is flowing steadily,
as the condenser is
merely short-circuited
by the closing of the
switch.

82, The switch arm,
continuing its rotation,
next separates from i
and thus breaks the
primary circuit. The
self-inductive action of
the primary coil tends
to keep the primary cur-
rent flowing after the
circuit is broken at i.
Without the condenser,
an appreciable spark, or

r — V-]

, ,„ _ a . .

■ tawj;tiMJWM iinLmtj"3?tiinEEt-j"nrntnTTL:H "

Fig. 29

arc, would be formed at i; but with the condenser, the energy
that would be expended in forming the arc is diverted into the
condenser, and the arc is prevented from forming, or at least
from being as intense and from continuing as long as it would
without the condenser. Thus, the current is stopped quicker;
that is, its rate of decrease from normal value to zero is much
greater. Hence, a greater electromotive force is induced in
the secondary coil. Furthermore, the energy received by the
condenser is given back to the primary circuit, producing a
flow of current through the primary circuit in a direction
opposite to that in which the battery sends current through it.

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§ 6 ELECTRIC IGNITION 47

This reversed current produced by the discharge of the
condenser induces in the secondary coil an electric current
that flows in the same direction as the current induced by
the decrease of primary current. Thus, the electromotive
force induced in the secondary winding is further increased
by this action. The difference of potential between the
terminals of the secondary coil is therefore greater when the
primary current is interrupted than when it begins.

83. The distance between the spark points of the second-
ary can be so adjusted that, while a, spark will jump between
them at the instant of breaking the primary circuit, none
will jump at the time of closing the primary circuit.

A safety spark gap is sometimes provided at k, Fig. 29,
to prevent possible damage due to an abnormally high
pressure in the secondary coil; otherwise, if the gap between
the points / is very wide, or if an excessive current is sent
through the primary coil, breaking down of the insulation
might occur. A spark jumps across the safety gap before
the pressure becomes higher than the insulation will stand.
In automobile practice, the width of the safety gap is about
i inch.

84. An induction coil that repeatedly opens and closes
the primary circuit by its own magnetic action, in conjunction
with the elastic action of a spring, is illustrated diagram-
matically in Fig. 30. The primary exciting current is supplied
by the battery B, and the circuit may be traced as follows:
From the positive terminal of the battery through wire Lj-
binding post P^-switch W-post E-screw AT-contact Z>-flat
spring F-wire P-primary coil P-wire P'-binding post
Pj-wire Lj to the negative terminal of the battery. On
closing the switch W, current flows momentarily through this
circuit and magnetizes the core C, which attracts the piece of
soft iron H attached to the end of the flat spring F and breaks
the contact at D. The current then ceases to flow, coreC*
loses its magnetism, and the reaction of the spring closes the
contact at D, thus permitting the current to flow again.

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ELECTRIC IGNITION

§6

These operations are repeated in rapid succession, thus con-
tinually changing the magnetism in the core C, and thereby
inducing in the secondary coil an alternating electromotive
force. The terminals of the secondary coil 5, which is wound
over the primary coil on the spool O, are connected to binding
posts 5i, Sj, to which may be connected the external circuit
containing the spark plug.

85. A condenser R consisting of instdated plates a, 6
has its terminals connected in the usual manner to the

III

Pio. 30

Opposite sides of the contact points where the primary
current is interrupted. The condenser discharge current,
which lasts but an instant, passes from a2 through £-W-P^
~Li-B-L2-P2-P'-coi[ P-wire P-b^, thus opposing the direc-
tion in which the current was flowing in coil P before the
contact at D was opened. This discharge imi^ediately stops
the current that was flowing in coil P, and may even start
an appreciable current in the opposite direction. The
magnetization of the core C is thus reduced almost instantly

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§6

ELECTRIC IGNITION

to zero, and an intense electromotive force is induced in the
secondary coil.

A condenser of suitable capacity for the coil with which it
is to be used must be selected. If this is done, the spark
at the contact maker when it opens the circuit through the
primary coil is almost entirely destroyed, and the induced
electromotive force is very much increased. When the cir-
cuit through the battery and the primary coil is closed by
the contact maker, the induced electromotive force in the
secondary coil is not large; it is when the contact maker
opens the circuit that the greatest effect is produced.

It is immaterial whether the positive or the negative termi-
nal of the battery is connected to the primary terminal P
of the coil.

The part HDF is
called the vibrator, ireni-
bier, or current inter-
rupter. The rate of
vibration of the inter-
rupter can be varied by
adjusting the screw K,

86. In order to get
better contact and a
more rapid separation
of the contact points at
the vibrator of an induc-
tion coil, an iini>act device is used on some coils. One
form of device is shown in Fig. 31 (a), in which a shows the
magnet pole and b the vibrator, which, in this case, is made
of a comparatively thin strip of tempered steel. This steel,
however, is not hard enough to remain a permanent magnet
after magnetization. Instead of having the contact point
located on the vibrator proper, a copper strip c is rigijily
mounted on the frame d, and a knock-off piece e is attached
to the vibrator. When the magnet attracts the vibrator
blade, the latter is drawn toward the magnet some distance
before the knock-off e strikes the end of the contact strip c

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ELECTRIC IGNITION

§6

and causes the contact points to separate. On account of
the velocity attained by the vibrator before striking the
contact strip, the break at the contact points is more rapid
than can be secured without the aid of some such impact
device. With this particular design of coil a stop / is pro-
vided to check the upward motion of the vibrator and pre-
vent its unnecessary vibration after the current is broken.
The ordinary adjustable contact screw is shown at g.

87. Another form of impact-break vibrator involving
the principle of operation just described is shown in Fig. 31 (b).
In this case, however, the contact strip c is placed on the side
of the vibrator next to the magnet a. The vibrator b is
perforated to allow the point of the adjusting screw e to

-5*^

Pio. 32

extend through it and press the contact strip c away from
the vibrator b when no current is flowing through the appa-
ratus, the frame of which is shown at d. When current
flows and the magnet a attracts the free end of the vibrator,
the latter moves down, gaining some velocity before it
strikes the contact strip, and suddenly breaks the circuit.

88. An exterior view of an induction coil with a mag-
netically operated vibrator and four terminal binding posts
is shown in Fig. 32. The binding posts a and b are the
terminals of the secondary coil. At c and d are shown the
terminals of the primary coil; at e, the trembler, or vibrator;
at /, a screw for adjusting the vibrator so as to bring the end

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§6

ELECTRIC IGNITION

carrying the piece of soft iron either nearer to or farther
away from the end of the core of the coil; at g, the head of
the adjustable contact screw whose point, generally platinum-
tipped, makes contact with the vibrator; and at A, one of
two small screws for clamping g firmly in its threaded hole
through the split yoke that supports it after it has been
properly adjusted. The induction coil and the condenser
are properly connected together and to the terminals, and
are firmly held in place in the box by a mass of paraffin,

f 9

v7 <?? V?

-^ i-

Fio. 33

which is poured in hot and allowed to solidify. One end
of the core of the coil is brought through the box just under
the trembler.

This four-terminal type of induction coil is not much used
on automobiles, because the three-terminal type is more
suitable. It is sometimes used for two spark plugs by
connecting a to the insulated part of one spark plug and b to
that of the other, the metal of the engine completing the

222—11

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52 ELECTRIC IGNITION § 6

connection between the plugs, which are connected in series
by this arrangement. The coil can be converted into a
three-terminal type by joining one of the primary terminals
to one of the secondary terminals.

89, Master Vibrator. — Instead of providing each coil
with a- vibrator, sometimes a single vibrating device, Called a
master vibrator, is used for a number of coils. Such
an arrangement, in which a master vibrator is provided for
use with four coils, is shown in Fig. 33. All four condensers
^1, ^2» ^8» ^4» have one of their terminals connected to the
master vibrator at p c, and each one has its remaining terminal
connected to that end of its own coil which is wired to one
of the contacts of the timer T. Thus, both the master vibrator
contact and one tim^r contact have a condenser connected
around them. The path of the discharge current from
condenser c^ may be traced from the lower side of the con-
denser through terminal p c, winding of the master vibrator
coil m V, battery connection p 6, battery A , frame of car
and engine, common connecting wire to the terminal p s oi
the left-hand, or No. 1, coil, through the primary winding
included between ps and p^, back to the condenser. The
discharge circuit of any other condenser can be traced in a
similar manner.

The master coil has a single winding, and is therefore
smaller than the double-wound induction coil and is com-
paratively inexpensive. It resembles a kick coil to which
a vibrator v is added. The timer in this case has its rotor r
insulated from the other parts of the apparatus. The current
from the battery passes through the master vibrator and
switch h to the rubbing contact piece of metal g, which is
fastened to an insulated part / of the timer, then through the
rubbing contact between the piece q to the metallic portion r
of the rotor, from which it passes successively through each
contact piece k^, k^y k^, and k^ to each primary coil, then to
the engine frame, and back to the battery. Ctirrent from
the secondary winding of each coil passes from 5 to the
insulated electrode of the corresponding spark plug i^, across

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5 6 ELECTRIC IGNITION 53

the air gap to the uninstdated electrode and thence through
the engine to the primary-secondary terminal p s.

If it is not considered necessary to protect the points in
the timer by condensers in parallel with them, the four con-
densers of the similar coils can be replaced by a single con-
denser connected aroimd the contact points of the vibrator
on the master coil.

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ELECTRIC IGNITION

(PART 2)

CURRENT-DISTRIBUTING DEVICES

SPARKING APPIilANCES

IGNITERS

!• The sparking device employed with what is variously
known as the touch-sparky wipe-sparky contact-sparky low-
tension^ or make-and-break system of ignition^ is commonly
called an Igrniter, which name distinguishes it from the
sparking devices used with the
jump-sparky or high-tension^ system
of ignition.

2. One form of lovr- tension
contact Igrniter is shown in Fig. 1.
The stationary electrode a is insu-
lated from the metal body of the ig-
niter by two pieces of steatite (soap-
stone). These are bored for the
electrode to pass through and are
coned outside to fitii;,the hole, which,
as shown, is much larger than the
electrode and tapers at the ends to suit the insulating plugs.
The rocker spindle b carries the contact finger r, which is
inside the combustion chamber and is connected by the
rocker spindle to the external arm d. This arm pro-

COrmiOHTBO by international textbook company. BNTBRBD at •TATIONERS* hall. LONDON

§7

Fig. 1

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ELECTRIC IGNITION

§7

vides a means for rocking the rigidly connected parts b, c,
and d.

3. The principle of operation, as well as the general
features of the mechanism for actuating this and similar
igniters, is shown in Fig. 2, view {a) being a front eleva-
tion and view (^) a side elevation. At a is shown a shaft

turning at one-half
the speed of the en-
gine; or, if the engine
is of the two-cycle
type, it turns at the
same speed, and may,
in fact, be the engine
crank-shaft itself . On
this shaft is a cam b,
frequently called a
snap cam, that bears
against a roller c, held
in contact with the
cam by the spring d
on the tappet rod e.
The lower end of this
rod, or plunger, is
threaded, so that by
adjusting the nuts at
/, and thus increasing
or decreasing the dis-
tance that the foot of
the rod extends into the socket g, the length of the rod and,
consequently, the width of the gap when the igniter points
separate, can be varied at will. When the roller c is in its
lowest position, the ball on the upper end of the tappet
rod e rests in a socket in the lever arm h (corresponding to
d. Fig. 1). This arm is secured to a rocking stem (as by
Fig. 1) that passes through the wall of the combustion
chamber, as shown by the dotted lines of the side elevation
in Fig. 2 (a). The inner end, which has a ground joint to

Pig. 2

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ELECTRIC IGNITION

prevent the gfases from blowing past it, is prolonged to the
finger /. This finger makes contact with an insulated
stem y, to whose outer end one of the wires of the electric
circuit is attached. The light spring k holds the finger i
against the stem /, except when the two are separated by
the pull of the head of the tappet rod e in the socket of the
arm h. Because the greater tension of the spring d over-
comes that of the spring k, the contact points are normally
out of contact except when the tappet rod is pushed up by

Pxo. 3

the cam. The adjustment of the tappet rod is such that
after contact has been made it leaves the socket of the
arm h and continues its upward motion a short distance, so
that, when the roller c drops off from the cam, the head of
the tappet rod strikes the arm h a smart blow, thereby
causing an abrupt separation of the contact points.

As shown, the roller c is mounted in a rocker-arm /, one
end of which is pin-connected to a second rocker-arm w,
which is operated by hand to control the time of ignition.
When the arm m is moved toward the right, as indicated by

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4 ELECTRIC IGNITION §7

the dotted outline n, the ig^nition is earlier than when it is in
the position m; when m is moved toward the left, to the
other dotted position o^ the ig:nition is made later.

4. A make-and-break Igrnlter desigfned to be operated
on cursent from a battery or a low-tension magneto, is
illustrated in Fig. 3. Fig. 3 (a) shows a longitudinal section
of the device, and Fig. 3 id) shows details of the interrupter
lever and magnetic core of the coil. The hexagon-headed
plug a is screwed into the engine cylinder in the same man-
ner as with a high-tension spark plug. The body d of the
plug contains a spool-wound magnet coil c and the upper end
of the interrupter lever d. The igniting current passes
through the magnet coil, and acts to move the interrupter
lever so as to break the circuit and form the spark at the
contact points of the igniter.

The interrupter lever d extends down into the part a, and
has at its lower end a contact point € that makes contact with
the stationary part /. The latter is part of a and is therefore
grounded, being electrically connected to the engine. The
magnet core ^ carries a knife edge at hy on which the inter-
rupter lever d rocks. A U-shaped spring / presses the inner
parts of its ends against both the core and the interrupter
lever, so as to keep the contact points e and / together,
except at the instant they are separated to form the spark.
The core ^ has a brass piece / inserted in it.

5. The electric circuit through the apparatus is from the
terminal k through the conducting plate /, rivet w, to the
terminal of the coil c, through the coil to its other terminal n,
which is in electric connection with the magnet core. From
the magnet core the current flows to and through the inter-
rupter lever d to the contact point e and thence to / and the
body of the engine.

When the timer closes the circuit, the current magnetizes
the core ^ and a magnet pole is thus formed in the region of
the brass insert j\ This pole attracts and draws toward it
the upper end of the interrupter lever d, thus rocking the
lever on its knife-edge support and moving the contact point e

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§7 ELECTRIC IGNITION 5

away from /. This breaks the electric circuit and causes a
spark at the contact points. The magnet loses its magnetism
immediately after the circuit is broken, and the contact
points are again pressed together by the U-shaped spring.
They are then ready for the next closing of the circuit by the
timer to form a spark for the next explosion.

The contact piece /, as shown in Fig. 3 (c) has a V-shaped
groove into which the contact e enters with a slight
wedging action. The interrupter lever is allowed a small
amount of side play, so that in case one side of the V of the
contact piece is fouled and does not make electric contact,
there is still the other side remaining with which suitable
contact may be made.

The body a is insulated from e by the steatite cone o and
mica plates ^. The makers of the plug recommend that
the part of the engine into which it is screwed be well
cooled by water.

SPARK PLUGS

6. The almost universal form of spark plug: for jump-
spark, or high-tension, ignition consists of a small central
wire or rod Ijhat passes through some kind of insulating
material. The insulation is in turn surrounded by a threaded
piece of metal or bushing that screws into a threaded hole
in the engine cylinder. The central wire, or rod, is thus
insulated from the external bushing, within a short distance
of which the central wire terminates. The space left between
the wire and outer metal bushing is the ^ap across which
the spark jumps. Being in contact with the metal of the
engine, the outer bushing of the plug forms part of the frame-
connected side of the high-tension circuit. Only the central
wire of the plug is insulated from the engine.

In some of the forms of high-tension spark plugs not
extensively used, the electrodes on both sides of the spark
gap are insulated from the engine, and in this way double
insulation is provided between the electrodes and terminals
of the wires leading to the plug. Two connecting wires are
necessary for each plug when double insulation is thus used.

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Pio. 4

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§7 ELECTRIC IGNITION 7

7. The width of the spark gap is generally about "sV inch
for spark plugs used in connection with induction coils pro-
vided with magnetically operated vibrators. In one or two
very unusual cases, the makers of such vibrator coils recom-
mend that the spark gap be as wide as W inch when the
batteries supplying current to the induction coil are new and
of full strength.

For use in connection with magneto-electric generators
and non-vibrator coils, or transformers, it is generally recom-
mended by the makers of such apparatus that the width of
the spark gap be from i^-r to A inch; these values correspond
approximately to .4 and .5 millimeter.

8. The material used for insulating the parts of the
spark plug from each other is usually either porcelain, mica,
or steatite. The threaded bushing is ordinarily made of
steel, brass, or bronze and the central wire of steel. The
inner end of this central wire is quite frequently terminated
with a piece of platinum wire.

As found on the market, the sizes of the threaded bushing
vary considerably. Many plugs are of the size that corre-
sponds to i-inch gas pipe; the outer diameter for i-inch gas
pipe is approximately i inch. The gas-pipe thread is tapered,
and for this reason no shoulder is required to make a gas-
tight joint between the plug and engine. In other plugs, the
thread is of uniform diameter, and a shoulder and copper
washer are provided, as shown in Fig. 4 (a), for making
the joint gas-tight. The thread is similar to that on a
machine bolt or screw. These plugs are about the same
size as those with the i-inch gas-pipe thread. Quite a
number of plugs in millimeter sizes are used; some are
larger and some are smaller than the 2 -inch gas-pipe thread
already mentioned.

9. Fig. 4 shows a number of spark plugs for jump-spark
ignition. In (a), the steel bushing a is the part that screws
into the threaded hole in the engine cylinder. At d is
shown the porcelain insulator; at c, a threaded bushing
for clamping the porcelain and packing into place; at d, a

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8 ELECTRIC IGNITION §7

packing ring of copper, asbestos, or some other suitable
material; at e, the central insulated wire, or electrode; and
at /, a binding-screw terminal for connecting the external
wire. The spark gap is between the curved end of the
central insulated wire e and the grounded wire g projecting
from the bushing a.

The construction of the plugs shown in (b), (^), {d)^ (<?),
and (/) is but little different from that shown in {a). What
is known as a closed-end plug is shown in (^), the points
a and b being located in the nearly closed end of the plug.
The point a is concentric with the plug-end opening into
which the point b projects from one side. The so-called open
type of the same plug is shown in {c) , the point a projecting
beyond the end of the plug, as shown. The point b can be
turned away from a to increase the gap between the points.
In the plug shown in (^), the point a is mounted in the
hexagonal head b of the insulated bolt c for conducting the
current and for keeping the plug tight, the spark bridging
the gap between the point a and the threaded shank of the
plug. In the plug shown in (<?), the insulated electrode a
resembles a star. The spark occurs between the projections
of the insulated electrode a and the threads of the grounded
electrode b. Jn the plug shown in (/), the insulated elec-
trode a is threaded and the opening b of the grounded
electrode is star-shaped. In the plug shown in (^), the
insulated electrode a is wrapped with sheet mica by and then
surrounded with mica washers c pressed closely together
under heavy pressure and held in place by a brass nut d and
washer. The grounded electrode e is fastened in the bush-
ing /. Spark plugs are sometimes protected against the
short-circuiting effect of moisture by means of a porcelain
hood, or cap, a. Fig. 4 (A). This cap has a recessed neck b
on one side to receive the wire c, which is connected to the
plug by a terminal link d in the manner shown.

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ELECTRIC IGNITION

AUXILIARY SPARK GAP

10. A spark plug whose insulation has become some-
what defective can sometimes be made to perform its service
by connecting in series with the gap at the spark plug a
device known as an auxiliary spark gap, two forms of
which are shown in Fig. 5. This device consists simply
of two insulated terminals a and d, with points separated by
an adjustable gap, usually about tV inch in length. In the
form shown in (a), the terminals are enclosed in a glass
tube c to prevent possible ignition of stray gasoline vapor.
This form is connected in the secondary circuit by means of
the connecting screws d and e. The form shown in (d) is
attached to the binding post of the spark plug itself, and the

Pig. 5

The

spark jumps from the point a to the binding post d.
base / is made of fiber.

When the primary circuit is broken by the timer, it
requires a short time for the induced current in the second-
ary circuit to build up to its full voltage; and, in order that
the full voltage may be reached, it is necessary that the first
small quantity of energy induced in the secondary shall not
be allowed to escape. If the spark-plug insulation is not
perfect, or if the plug is sooted, the charge first induced
leaks away either through the insulation or over the soot
deposit, and the voltage does not become great enough to
force the current across the gap and produce a spark. By
the use of an auxiliary spark gap outside the cylinder, the
secondary circuit is held open, this leakage is prevented, and

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10 ELECTRIC IGNITION §7

the induced current builds up to its proper voltage. Thus,
when the gap is finally bridged, the entire energy of the
induced charge is employed in producing the spark.

TIMERS

11. Timers, or primary commutators, as they are
commonly called, are devices for closing the ignition circuit
at some prearranged point or points in the revolution of the
crank-shaft, keeping it closed sufficiently long to insure igni-
tion, and then opening it, no matter whether the engine is of
the single or of the multicylinder type. The principle of
operation of all timers is practically the same, but the length

Pio. 6

of the time of contact varies, and in some cases the time of
contact is so prolonged that an extremely short life of the
battery is the result.

Almost innumerable forms of timers are in use. One of
the features of chief importance is the method of making
contact between the rotor and the stationary member.
Sliding contact is used to a considerable extent, and steel
balls are also used for contact. In most cases the rotor is
electrically connected to the driving shaft, but in some
designs it is insulated from the machinery and frame of
the car.

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§7 ELECTRIC IGNITION 11

The most essential requirement to be met by a timer is
that, for a given setting, it shall always close the primary
circuit at the same instant relative to the movement of the
engine piston. This is called synchronous operation. Many
timers fail in this respect after some service, the failure gen-
erally being due to worn or loose parts that can move to some
extent without restraint. With the timer illustrated in Fig. 6
such failure is not likely to occur in case of wearing at the
roller and pin that holds it, because the spring attached to
the arm always keeps these parts pressed together. Parts,
such as a roller and its pin, that are not pressed together in
this manner are liable to give trouble when wear occurs.
Also, wear between the stationary parts and the shaft of the
timer may cause some irregularity in the time of ignition.

12. The timer shown partly in section in Fig. 6 closes a
primary electric circuit at each instant that a spark is to be
produced in the engine. The casing, or housing, of this timer
consists of a large wood-fiber disk a, with a thick raised rim b,
in which are embedded four brass contact pieces c, each of
which i§ provided with a terminal for connecting to its
proper spark coil. The shaft that supports the timer runs
through the disk a, which has a bearing on the shaft and
carries a hub d, to which is pivoted a lever e. One end of
the lever e carries a roller / that runs against an internal
ring b and makes contact with the insulated segments c, A
spring g connected to the other end of the lever e insures
good contact. An arm h projecting from the body of the
timer is provided for making connection to a system of links.
These links prevent the rotation of the disk a, and at the same
time afford a means of changing the instant of ignition
through movement of the hand-operated spark control lever
at the steering wheel, not shown. A cap is provided for
covering the parts of the timer and protecting them from
dust. This cap also affords a means of retaining oil or
grease for lubrication.

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ELECTRIC IGNITION

§7

DI8TRIBUTOBS

13. Distributors, or secondary commutators, are

devices used with the jump-spark system of ignition for
delivering the high-tension, or secondary, current generated
in a single induction coil to all the spark plugs, the use of a
separate coil for each plug thus being obviated. Except for
the rotor of the timer 7", as shown in Fig. 7, the primary, or

low-tension, circuit is identical with that for a single spark
plug. For a four-cylinder engine, instead of four contact
points, as in the ordinary timer, the timer rotor r has as
many contact points as there are spark plugs, so that the
primary circuit is closed at the single insulated contact piece k
of the timer as many times per revolution of the timer as
there are spark plugs.

The high-tension terminal of the spark coil s is electrically
connected to the rotary arm d of the distributor. This dis-
tributor arm revolves about the axis w, and is insulated from

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§7 ELECTRIC IGNITION 13

all other parts of the apparatus and of the automobile. The
spark plugs are connected to stationary insulated terminals
i, 2, 5, 4 of the distributor. As the distributor arm turns
about its axis, its broadened end passes successively over
these terminals, either making metallic contact with them or
coming very close to them. The rotor r of the timer and
the arm d of the distributor rotate at the same speed, so
that when the timer closes the primary circuit, the end of the
distributor arm is over one of the terminals i, 2, 5, 4. The
high-tension current passes between the distributor arm and
the terminal that it is over, and is thus directed to the cor-
responding spark plug. Through the rotation of the dis-
tributor arm, the current is distributed successively to the spark
plugs of a four-cylinder engine in either the order i, 2, 4, 3 or
5, 4, 2, 1, according to the direction of rotation of the arm.

Since the current passing between the distributor arm
and the stationary terminals has sufficient tension to jump
the gap at the spark plug, it will also jump a small gap
between the distributor arm and terminal in case they
do not touch each other. In fact, a small air gap here is
sometimes considered an advantage for the reasons given in
connection with the description of auxiliary spark gap
devices in Art. 10.

The timer rotor r and 'the distributor arm d are generally
mounted on the same spindle, or shaft, but they are
thoroughly insulated from each other. If they are mounted
on separate shafts, the timer rotor may have only two con-
tact points and may rotate twice as fast as the distributor
arm; or, it may have only one contact point and may rotate
four times as fast as the distributor arm. The free end of
the distributor arm is broadened circumferentially, in order
that some part of it will always be over one of the cor-
responding terminals when the timer closes the primary circuit,
although the contact piece k of the timer is rocked through
a considerable arc (45° or so) to vary the time of ignition.

14. Spark coils of both the transformer, or non-vibrator,
type and the vibrator type, are used in conjunction with a

222—13

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ELECTRIC IGNITION

§7

distributor. When the vibrator type of coil is used, the
work for the contact points at the vibrator, is somewhat
arduous, because the single vibrator must perform as mtich
work as the four vibrators in an individual spark-coil system

for four spark plugs. Under
this condition, the vibrator
contacts are much more liable
to become burned and fused
than when the work is divided
among the four vibrators of
the individual-coil system.

If the coil fails to operate
because of this or any other
reason, ignition current is
cut off simultaneously from
all the spark plugs, and, un-
less provided with more than
one ignition system, the en-
gine under ordinary condi-
tions will stop immediately.
The possibility of this occur-
rence is recognized by the
makers of such ignition de-
vices, and a spare coil is often
provided in the box enclosing
this part of the ignition ap-
paratus.

In a vibrator coil used in this
manner, the condenser can
be connected in parallel with only the vibrator contact points.
The timer contacts are thus left without the protection of a
condenser, but this is common practice for battery currents.

15. Commonly, the distributor is mounted on the same
shaft as the timer. Fig. 8 shows this arrangement in sec-
tion and elevation. The primary contact is made by a
steel ball a, held in place by a spring, as shown. The
sleeve b and contact cam c are carried on a shaft turning

Fig. 8

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§7

ELECTRIC IGNITION

at one-half the speed of the crank-shaft of a four-cycle
engine. The cam has four lobes for a four-cylinder
engine of this class. The secondary current is led to
the binding post d, through which it travels, by way of
the contact ball <?, to the brass strip / that runs over the
hard-rubber surface g, and makes contact with the flat-
headed screws h embedded therein. These screws carry
the current to the several spark plugs.

Efficient insulation between the primary and the secondary
is secured by the long, hard-rubber stem / on which the brass

Fio. 9

strip / is carried. The casting j is rotated by the arm k
to advance or retard the spark. It is evident that a rock-
ing movement of this arm either advances or retards both
pHmary and secondary contacts alike. A ball bearing / is
shown between the spindle and the part c.

16. In the comblnecl timer and distributor shown
in Fig. 9, the shaft a carries at its extreme end the timer
cam b, which has as many lobes as there are spark plugs to
be supplied. These lobes successively make contact with
the steel plunger c. This plunger is supported in a hard-
rubber casing d, and by means of a sleeve is fastened on a for
rocking according to the spark advance required. Attached

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ELECTRIC IGNITION

§7

to a by a taper pin is a hard-rubber barrel <?, carrying a con-
tact ring / extending clear around it and connected through
a longitudinal strip with a single contact segment near the
left-hand end of e. The secondary current is carried to the
ring / by the contact plunger g, and four other plungers
mounted in d make contact successively with the segment
connected with /. The hard-rubber mounting affords effi-
cient insulation. To the right-hand end of d is screwed a
metal ring h, from which projects an arm for rocking d to
advance or retard the spark. The light casting i affords a
bearing for the shaft and for the ring h, and can be screwed
to any convenient support, the shaft a being operated by a
chain or flexible shaft driven from the cam-shaft. A glass
front/, through which the action of the timing cam may be
watched, is provided.

17. AtAvater-Kent Spark Generator, — A combined
primary, or low-tension, timer and secondary, or high-tension,
distributor, the design of which diflEers considerably from

that of ordinary types, forms
the principal part of the appa-
ratus shown in Fig. 10, which
is known as an Atwater-
Kent spark generator.
Besides the combined timer
and distributor, this device
includes a coil of the trans-
former, or non-vibrator, type
and a condenser. The whole
mechanism is enclosed in a
box, or case, a, so as to form
a single unit that is bolted to
the dash. On the bottom of
the box, at the right, are two
binding-post terminals, to
which are attached the wires
from the zinc and carbon terminals of a dry-cell battery.
The negative, or zinc-plate, terminal wire is connected

Fig. 10

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§7 ELECTRIC IGNITION 17

to the binding post nearest the dash, and the wire from the
carbon-plate terminal is attached to the binding post shown
at b. The secondary is grounded within the device, and for
this reason no ground wire is necessary.

The timer, or primary contact maker, the distributor, and
the spark-advancing device are carried by a single vertical
shaft c in the left-hand side of the box. This shaft is driven
from the cam-shaft, timer shaft, or other rotating part of the
engine by means of gears and shaft with universal joints.
With four-cycle engines, this shaft rotates at the same speed
as the cam-shaft, but with two-cycle engines, it is driven at
the same speed as the crank-shaft.

18. When the primary circuit is broken by the contact
maker, the induced secondary current passes from the coil in
the right-hand side of the box to the distributor shaft c
through a brush in the brush holder dy the brush being
held in contact with the shaft by means of a spring. From
the shaft Cy the secondary current is delivered by some one
of the four brass distributor blades e to some one of the four
secondary terminals and connected binding posts /, to which
are attached the wires leading to the spark plugs. These
wires are carried through holes in the dash and the back of
the box. The distributor blades ^, which do not touch the
terminals, are insulated from the rest of the shaft, and the
secondary terminals to which the binding posts / are attached
are also insulated. Opposite each of the secondary terminal
binding posts is a spring-actuated button g. This button,
when pressed inwards, grounds the spark for the corre-
sponding cylinder of the engine, the plugs of which may
thus be tested. When trouble from skipping is experienced,
the cylinder that misses may be easily located by alternately
depressing the four cut-out buttons; the one whose depres-
sion does not affect the firing of the other cylinders corre-
sponds to the cylinder that misses.

The spark plug of the first cylinder, in which the charge is
to be exploded, is connected to the terminal opposite the
upper distributor blade, the plug of the second cylinder is

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ELECTRIC IGNITION

§7

connected to the terminal of the distributor blade that next
comes to its terminal, and so on. The spark is advanced
or retarded by means of a spiral sleeve actuated by the
shaft >^, so as to turn the upper part of the shaft c^ where
the contact device, or timer, within the case / is attached.
For starting the engfine **on the spark," the contact maker is
provided with a starting lever that has a button j. This

Fig. 11

button, when pressed, makes contact, and when released,
produces a spark in the cylinder that happens to be in
communication with the distributor. The contact should be
made and broken by a tapping motion of the fingers on the
button y. The cover over the contact maker is held in place
by a wing nut k, while the generator box is fastened to the
dash by means of bolts passing through holes /, of which
there are two on each side. The battery switch m is mounted

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§7 ELECTRIC IGNITION 19

on the front of the box, as shown, the removable switch
plug n being located to the right of the switch lever o. An
oil tube p provides for lubrication, while the clamping collar q
provides a means of setting the time of the spark.

19. A plan view of the mechanism of the primary con-
tact maker, or timer, of the Atwater-Kent apparatus is
shown in Fig. 11 (a), different positions of the working
parts being shown in {b) and {c). There are three moving
parts, namely, the shaft a, the snapper b, and the pivoted
contact arm c. In the end of the shaft «, which is the upper
end of the shaft c. Fig. 10, are four notches that form a
ratchet. This ratchet engages the claw at the end of the
snapper ^, which is a light piece of tempered steel that is
guided in its movement by slots in the bronze base de and
is pulled by the spring / against a spring-wire stop g when

released from the notches on the shaft. The contact arm c

is normally held in the position shown in Fig. 11 {a) by the
spring h. The shaft «, turning counter-clockwise, draws
the snapper b into the position shown in (^), the claw of the
snapper riding up out of the notch of the ratchet on to
the rounded part of the shaft, as shown in {c). In this way,
it acts as a wedge between the shaft and the steel hook / of
the contact arm, which is pivoted aty, and brings a platinum
point in the flat copper spring k into contact with the
insulated stationary contact screw /, thus closing the primary
circuit. Under the pull of the spring /, the snapper claw
is then quickly snapped into the next notch of the shaft,
releasing the hook i and thereby suddenly breaking the
contact at the platinum points on k and /. The snapper
and contact arm thus come to rest in their normal positions,
as shown in Fig. 11 (a).

With the engagement of the snapper claw by the next
tooth of the ratchet, the process of making and breaking the
circuit is repeated, the period of contact being the time
required for the snapper b to slide past the hook /. The
duration of contact, which is always orief, may be varied by
turning the contact screw /. No spark is produced in

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ELECTRIC IGNITION

§7

turning: the shaft a in a direction opposite to its normal, or
counter-clockwise, rotation, because the snapper will clear
the hook of the contact arm when the shaft is given a clock-
wise rotation. This non-reverse feature is of value with
two-cycle engines, which will start backward **on the spark"
as readily as forward when an ordinary timer is used. There
is nothing about the device that requires adjustment, except

the contact screw /, a close setting
of which prolongs the duration of
contact, because the contact is
sooner established on return of the
snapper. Adjustment of the con-
tact screw permits of a light con-
tact with a fresh battery, while with
the maximum length of contact,
cells that would ordinarily be con-
sidered depleted may be utilized,
because there is no waste of
energy in the production of more
than one spark, which is all that
is needed to ignite a combustible
mixture. In the ordinary service,
after adjustment for use with a fresh battery, the contact
points should be brought nearer together by giving the
contact screw / a quarter or a half turn every 500 miles.

Pio. 12

20. In Fig. 12 is shown a more compact form of the
primary contact maker and the distributor elements of the
apparatus shown in Fig. 10. In this case, the non-vibrator
coil, condenser, and switch are arranged in a separate unit
attached to the dash. This device is adapted for use on cars
where it is inconvenient to install the spark generator, and
takes the place of an ordinary timer on any convenient half-
time shaft. The hard-rubber distributor casing a carries
four posts d, to which the spark-plug cables are attached.
Two primary wires are run in the cable Cy from the coil to
the contact maker, and a central post d receives the high-
tension current from the coil and transmits it to the dis-

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§7

ELECTRIC IGNITION

tributor blade. This blade is fastened to a hard-rubber
block removably mounted on the contact-maker shaft. For
advancing and retarding the spark, the body of the contact
maker is actuated by the lever e in the usual way.

SWITCHES

21. Small hand s^vitclies, such as are used on auto-
mobiles in the primary circuit for two batteries, are shown in
Fig. 13. In the switch shown at (a), the positive terminals
of the two batteries are attached at the back to the con-
tact points a and b, respectively, so that, when the switch
arm c is in contact with either contact point, current will flow
through the switch
arm c and plug flf, shown
in full in the side
view (^), to the spark
coil, and from thence to
the timer and through
the grounded timer
shaft back to the
battery. The switch
arm, or lever, c. Fig. 13
(f), is removable, and
is shown separated
from the base of the
switch, Fig. 13 {d),
to which it belongs.
When put into use, the
pin, or plug d is inserted
in the round hole shown
just back of the base
plate. When the pin
is thus inserted, the
wedge-shaped contact
point on the switch
arm c can be brought
against either the contact piece a or the contact piece b or
between the two at the space marked e. The part with which

Pio. 13

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ELECTRIC IGNITION

§7

the plugf d is in contact is generally connected to the wire
leading to the induction coil. One battery wire can be con-
nected to a, and the other to b. Either battery can then be
put into service by. bringing the lever c, Fig. 13 (r) , over the
switch terminal belonging to that battery. By putting the

(a)

(h)

Fio. 14

contact piece of c in the space e between a and b, so that
the sides of the wedge press against both of these parts, the
batteries will be in parallel. A small notch near ,the middle
of each of the contact pieces serves to hold the lever in
position when the knife edge bears in the notch.

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§7 ELECTRIC IGNITION 23

22. A tTvo-battery si;vitcli having five positions for its
lever arm, including the off-position, is shown in Fig. 14.
The four working positions correspond to: (1) battery A in
circuit alone; (2) battery ^ in circuit alone; (3) batteries-^
and B in parallel; and (4) batteries A and B in series.

A plug a fits into the hollow pivot of the switch arm. The
withdrawal of this plug breaks the electric circuit, so that the
switch becomes inoperative. In (b) is shown the switch
connections for an individual-coil, high-tension ignition
system. The switch is generally placed near the spark
coil C from which the secondary wires are carried to the
spark plugs D. A wire is led from the binding screw a to one
primary terminal of each spark coil. In this case there are
fom: coil terminals. When the switch arm is on contact
button by the circuit is open; when on Cy battery A only is cut
in; when on dy battery B only is in circuit; when on ^, the
batteries are operating in parallel; and when on /, the batteries
are in series.

The connections, in addition to those already given, are as
follows: From the carbon plate of the right-hand end cell of
battery Ay a wire is carried to the binding screw Cy the wire
from the carbon plate of the right-hand end cell of battery B
being carried to the binding screws, under which is a link, or
contact strip, s connecting with the contact points d and /.
Thus far, the same letters of reference apply to similar parts
in {a) and {b). A wire from the zinc of battery A is con-
nected to the binding screwy attached to the metal plate hy
and a wire from the zinc of battery B is connected to the
binding screw i attached to the metal plate /. In a fiber
plate k fixed on the post a, Fig. 14 (a), so as to turn with it
when the switch arm is shifted, are mounted three contact
pins /, nty and w, Fig. 14 (b)y that slide on the metal plates h
and y. These pins are electrically connected by means of a
wire laid in a slot in the fiber plate k and soldered to
the pins.

23. When the end of the switch arm rests on the contact
point Cy current flows from battery A to c, then through the

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ELECTRIC IGNITION

§7

switch arm to « , thence by wire p to coils C, and by gfrounded
connections q and r back to battery A, When the switch
arm is on d^ current flows from battery B to ^, thence through
the metal plate s to d, through switch arm to a, to coils C to
grounds q and r, wire / to binding screwy and plate h, pin /,
wire 0, pins m and n, plate y, screw i and wire «, back to
battery B. When the switch arm rests on e, it also makes
contact with the auxiliary contact point v. Fig*. 14 (a), which
is connected to r, Fig. 14 (^), by means of the metal plate w.
The two wires from the carbon plates of the right-hand end
cells of the two batteries are thus connected together, the
two wires from the zincs of the left-hand end cells of the

two batteries being con-
nected by means of the
contact pins /, w, and w,
wire 0, plates h and /.
The batteries being thus
connected up in parallel,
current flows through
binding screws and switch
arm to a^ then to coils C,
grounds q and r to bat-
tery A, and to battery B^
by way of wire /, binding
screw^^, plate h, pins /, m,
and n, and wire o, plate /, screw /, and wire «. When
the end of the switch arm is shifted into contact with /,
the pin / is moved out of contact with the plate h, while the
pin n makes contact with the metal plate x, thus connect-
ing the carbon of battery A to the zinc of battery B, and
thereby placing the batteries in series. Current then flows
through the wire from the carbon plate of the right-hand
end cell of battery B to e, then through plate s to /, through
switch arm a, to coils C, to groupds q and r, back to the
left-hand end cell of battery Ay thus completing the circuit.

Pig. 16

24. A switch for use where two sources of current are
available, as where storage batteries and coils are installed

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§7

ELECTRIC IGNITION

together with a magneto, is shown in section in Fig. 15.
By throwing the switch handle a to one side, the magneto
circuit is closed and the magneto is in operation; throwing
the switch handle to the other side cuts out the magneto,
closes the battery-and-coil circuit, and places the batteries
and coils in operation. The ball contacts b are held against
the contacts c by the springs d, and are in electrical connec-
tion through the strip e. Wires from the two sources of
current are led to the binding screws / and g^ the common
circuit-completing wire being attached at h.

25. A sln^le-tliroTv^, two-pole, knife switch, or
blade switch, is shown in Fig. 16 (a). The two blades a
and b are insulated from each other, and hinge on pins
through the posts c and d. The lips of each of the other
two posts e and /
press against the
blade between them
with a spring action,
so as to make good
electrical contact. As
ordinarily used, one
side of the switch, as
f, a, and e, is inter-
posed in one side of
an electric circuit,
and the other side d^
b, / in the other side
of the circuit. Thus,
if used on a battery
circuit, the positive
wire from the battery
can be connected to c, and the negative wire to d. The
wires leading out to the other part of the circuit are then
similarly connected to the posts e and /, respectively. When
the switch is opened by lifting the handle and blades, both
sides of the circuit are broken. The term two pole is used
because both sides of the circuit are connected to the switch.

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26 ELECTRIC IGNITION §7

26. A double-tlirow, two-pole, blade switcli is

shown in Fig. 16 {d). It differs from the single-throw
switch just described in that it has another pair of posts to
which a second pair of wires can be connected. If used with
two batteries, either of which is to supply current to a piece
of electrical apparatus, the wires from one battery are con-
nected to the posts e and /, and the wires from the other bat-
tery to posts ^ and h. The connections to the apparatus are
made at c and d. Either battery can be put in circuit with
the apparatus by throwing the blades to the corresponding
position. The term double-throw is applied to the switch
because it closes a circuit in either of two positions.

Blade switches are not much used on automobiles, but
apparatus for charging storage batteries is generally equipped
with them.

INSULATED WIRES AND WIRE TERMINALS

27. The insulated conductors used in automobiles are
generally made in the form of wire cables having a rather
large number of strands. The chief difference between those
for high-tension current and those for low-tension current is
in the thickness and electric pressure-resisting qualities of

the insulation. From an electrical standpoint, the high-
tension cable does not need near so much copper as the low-
tension one, but is made heavy enough to give it strength
to meet mechanical requirements.

28. Typical insulated copper cables are shown in
Fig. 17. The primary, or low-tension, cable is shown in («).
The wire core of the cable consists of forty strands of No. 30
tinned copper wire. The insulation consists of one layer

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§7 ELECTRIC IGNITION 27

of high-gfrade vulcanized rubber a, and the protective cov-
ering consists of two braids c and d covered with two layers
of enameled coating baked on. It would take about 12,000
volts'to puncture this insulation. The core of the high-tension
cable (^) is the same as that of the low-tension cable. The
insulation consists of three layers of rubber a, by c vulcanized
together. The rubber is protected by two braids e and /,
covered with four coats of enamel baked on in steam-heated
ovens. The enamel forms a flexible, insoluble film that pro-
tects the rubber from heat, oil, and water, and the braid
protects the cable from mechanical injury. More than 40,000
volts is necessary to puncture the insulation of this cable.

29. Copper or brass terminals are generally attached to
the ends of insulated wire conductors. For the primary low-
tension cables, it is essential to have good metallic contact.
This is readily secured by using a drop of solder to fasten
the wire and terminal together at one point. It is not neces-
sary generally that the solder shall make a strong mechanical
connection. On high-tension ca-
bles, soldering between the cable
and terminal is never necessary,
so far as the electrical connections
are concerned. The high-tension
current will jump any ordinary fig. is

small air space that may occur between the different metallic
parts. Soldering may be desirable, however, in some cases,
to hold the parts together. The terminal piece should be
provided with clips, a ferrule, or some corresponding device
that will firmly grip the insulation and thus relieve the
mechanical stress on the wire core, so as to secure a connec-
tion not liable to breakage.

30. Good battery connectors may be made up from No. 16
flexible lamp cord in 8-inch lengths. The cord is untwisted for
the purpose, and each length makes two connectors. The ends
of the cords are scraped for a length of about 1 inch, and the
bare wire twisted and 'doubled on itself. The wire is then
slipped through a terminal or copper connector of the form

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§7

shown in Fig. 18, the bare end being run through the stamped
loop a. The loop is then hammered flat, the wire doubled back
on itself, and the clips h bent over the insulated part of the wire
with a pair of pliers. The wire is then coiled around a lead pencil.
If the binding posts on the battery cells show a tendency
to work loose, the nuts may be locked with nuts taken from
discarded cells. If, however the wire connections are flex-
ible, such as those just described, and the cells do not shake
about, there will be little tendency on the part of the nuts
to work loose.

CURRENT-MEASURING INSTRUMENTS

31. ATtimeters and Voltmeters. — In connection with
automobile ignition, the instruments used for measuring the
strength of current in amperes, called ammeters, and pres-
sure of current in volts, called voltmeters, are generally
of small size and of convenient form for carrying, frequently
being made to resemble a watch. Their accuracy need not
d be very great. Such instruments

^M are often combined into one,

measuring both the current
strength and the pressure, in
which case they are called
voltammeters.

32. A simple form of instru-
ment for measuring either volts or
amperes, or both, according to the
winding of the coil through which
the current flows in any case, is
shown in Fig. 19. For con-
venience of description, it will first
be assumed that the instrument
is constructed for measuring amperes of current. A coil
of insulated wire a is wound on a" stationary spool, as shown.
A piece of soft-iron wire, or rod, b is rigidly fastened to the
spool on which coil a is wound, and a spindle c is pivotally
supported by the stationary parts d. At e is shown a sheet-

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§7 ELECTRIC IGNITION 29

iron vane carried by the spindle c, and at /, a spiral spring,
one end of which is connected to the spindle and the other
to the stationary spool of the coil. All the parts except b
and e are of brass or some other non-magnetic material.
The spindle c and vane e are free to turn on the conical
bearings at the ends of c, except that this motion is resisted
by the spiral spring /. The mounting of the spindle c is
somewhat the same as that of the spindle of the balance
wheel of an ordinary time-keeping watch. In the position
of the parts e and c as shown, there is no tendency for the
spring / to rotate c and e in either direction.

When an electric current flows through the coil a, both the
iron wire b and the vane e become magnetized. The action
of the magnetizing current is Such that the poles formed in
these two parts are at adjacent ends. Thus, if the upper
end of ^ is a north pole, the upper end of e will also be a
north pole; and the lower end of each will be a south pole.
The adjacent magnetic poles repel each other. This repul-
sion causes e to swing away from b in the direction indicated
by the arrow. This movement of e and c is resisted by the
spring /. The larger the current that flows through the coil,
the greater will be the movement thus given to e. By con-
structing the apparatus in suitable form, the rotation of e can
be made approximately proportional to the amotmt of current
flowing through the coil a, thus affording a practical means
of determining the strength of current. As such instruments
are ordinarily constructed, an index finger, resembling the
hand of a clock, is attached to the spindle c and registers on
a scale suitably divided and marked to indicate the amount
of current flowing. Such an ammeter is connected in series
with the apparatus through which the current to be measured
is passing, so that all the current flows through the ammeter.

33. If the instrument is to be used also as a voltmeter,
then another winding g of thin wire and many turns, so as
to have a high electric resistance, is added. When used to
measure voltage within the range of the instrument, the
resistance of this winding is thus made high enough to pre-

222—13

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ELECTRIC IGNITION

§7

FiO. 20

vent the flow of current through it to an extent that is
appreciable in proportion to the current capacity of the

battery or other source of elec-
tric current pn which pressure
measurements are taken.

The reading of the volts
is taken by the same index
pointer as is used for am-
peres, but another scale is used,
as shown in Fig. 20.

34. Small, portable instru-
ments for measuring the amper-
age and voltage of electric cir-
cuits are useful in determining the condition of batteries, the
current consumption of coils, and the behavior of dynamo-
electric generators that are used to furnish direct current for
ignition purposes. Such an instrument as is shown in Fig. 20
is used in testing bat-
tery cells by touching
the part marked carbon
to the carbon (positive)
terminal of the cell, and
the insulated cable a
to the zinc (negative)
terminal, which short-
circuits the cell. The
instrument indicates
amperes only when the
button b is pressed.
The button should be
pressed for an instant
only, barely long
enough to allow the
needle to come to rest, as a cell is very rapidly depleted by

short-circuiting.

Fio. 21

35. Hoyt Voltammeters. — An instrument of higher
grade than that illustrated in Fig. 20, and known as a Hoyt

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§7

ELECTRIC IGNITION

voltainmeter, is shown in Fig. 21. It is provided with
one voltmeter scale, reading from to 10 volts, and two
ammeter scales, one reading from to 30 amperes, for
testing battery cells, and the other from to 1.5 amperes,
for testing the current consumption of spark coils. The
binding post a is for the positive connection, whether for
amperage or voltage testing, the right-hand post b being
negative for the 30-ampere scale, post c negative for the
voltage scale, and post d negative for the 1.5-ampere scale.
For making test connections, two cable connectors are sup-

Pio. 22

plied, one for tests requiring the use of the high-amperage
scale and one for tests with the low-amperage scale.

This instrument operates on what is known as the
D'Arsonval principle. A permanent magnet is employed to
create a strong magnetic field of practically unvarying inten-
sity. Within this magnet a rectangular coil of fine wire,
wound on a centrally pivoted, aluminum, open-frame bobbin
mounted between the pole pieces of the magnet, is made to
rotate against the opposing influence of a spring by the cur-
rent that passes through it. Attached to the coil bobbin or
frame is a pointer that moves over a scale so graduated as

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ELECTRIC IGNITION

§7

to indicate the strength (amperage) or the pressure (voltage)
of the current that causes a deflection of the coil from its
normal or zero position.

36. Another Hoyt instrument, operating on the same
principle as the one just described, but designed to form an
integral part of the ignition circuit, is shown in Fig. 22. It
consists of an ammeter, at the left, and a voltmeter, at the
right, mounted on a common base that is permanently

(.ri fii^WiiK

azD 6^
OOO

Fig. 28

attached to the dash of the automobile by screws, provided
the dash is of wood. In case the dash is of metal, the
instrument is attached to an insulating block on the dash.
Making the instrument a permanent part of the ignition circuit
puts the operator of the car in. possession of a continuous
and visible record of performance; in this way, faults that
could not otherwise be quickly traced and eliminated can be
readily detected and remedied under working conditions,
oftentimes while the car is in actual operation.

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§7 ELECTRIC IGNITION 33

37. In Fig. 23 is shown a conventional diagram that
illustrates how the voltammeter shown in Fig. 22 is connected
up. As will be observed, the carbon, or positive, terminal
of the dry-cell battery A, and the positive, or plus( + ),
terminal q£ the secondary, or storage, battery B^ are connected
to terminals of the coil c. From these terminals wires are
led to the timer dy by means of which the primary circuit is
closed. From the block carrying the contact screw of either
of the units of coil ^, a wire is led to the right-hand binding
post of the voltammeter. The zinc, or negative ( — ), termi-
nals of both batteries are connected to the center, or negative,
binding-post terminal of the voltammeter, instead of the
ground, as is customary. The ground, or return-circuit, wire
is attached to the left-hand bindmg post of the voltammeter.
Current from the primary dry-cell battery Ay or from the
secondary battery By whichever may happen to be in use at
the time, passes through the primary winding of the coil c
when the*circuit is closed by the timer d. This current also
passes through the voltammeter e and engine /, through
which the return circuit is completed, as is indicated conven-
tionally by the dotted line from the timer shaft to the ground-
wire connection on the engine. The direction in which the
current flows is indicated by the arrows. From the coil Cy
through the wire attached to the right-hand binding post, cur-
rent flows into the voltmeter and out to the center binding
post, and from this point it flows back to the battery. When
the timer closes the circuit through the coil, a part of the
current that flows through the timer shaft and ground wire
attached to the engine and left-hand binding post, passes
into the ammeter and out to the center binding post and then
back to the battery. Most of the return current passes
directly from the left-hand binding post to the center binding
post through an insulated by-pass or short-circuit connection,
or shunt, on tha back of the mounting.

Ordinarily, the method of wiring shown in Fig. 23 will cor-
rectly connect the instrument in circuit. However, with some
types of coils, for example, the Kingston, the wire leading to
the right-hand, or voltmeter, binding post must be attached

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ELECTRIC IGNITION

§7

to one of the hexagon nuts on the bottom of the coil box.
Instead of the contact-screw block, the copper or brass strip,
by means of which the several units of some standard makes
of coils are connected on the top, may be also used as a place
of attachment for the wire leading to the voltmeter^

IGNITION SYSTEMS

liOW-TENSION IGNITION

38. Make-and-Break, or Contact^ System, — If the

ends of two wires forming part of an electric circuit are
brpught into contact, thereby closing the circuit, and then
quickly separated, a bright spark will be produced as the
contact is broken. This phenomenon underlies the opera-
tive principle of what is variously known as the toucli-
sparky ipvipe-spark, loi;v-tension, contact, or make-
and-break, system of ig^nition, with which it is necessary
first to complete the electrical circuit through the spark-
producing me'chanism, or igniter, and then break the circuit
to obtain a spark for igniting the charge.

39. A contact-ignition system with battery current is
shown diagrammatically in Fig. 24. The battery is illus-
trated conventionally
at A and the kick coil
at b. The igniter
contact points c and d
go inside the cylinder,
and the stationary rod ,
or electrode, ^, which
carries the contact
point f , is surrounded
by mica or steatite
insulation /, where it

passes through the cylinder wall. The rocker-arm g is con-
nected to the spindle h, which passes through the cylinder
wall and carries the outside member /. The three parts d, g.

Fig. 24

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§7 ELECTRIC IGNITION 35

and h are rigidly fastened together, and h is free to turn, or
rock, in the stationary metallic bearing that surrounds it.
A leaf spring / is rigidly attached to /, and engages with the
ignition timer cam k^ whose shaft / is supported by some
stationary part of the engine. One terminal of the battery
is connected to the frame of the automobile at m. The
dotted line indicates the electric connection between m and h
through the frame and other parts in metallic contact with
the frame. At n is shown a hand switch that, when closed,
completes the electric circuit, except at the contact points
c and d» This switch is kept permanently closed during the
operation of the system. The coil-spring p pulls the contact
point d away from c,

40, When the contact points are pressed together, the
path of the current is from the battery A through the kick
coil ^, the switch «, to the stationary rod e of the igniter,
then to r, dy g, and ^, and through the parts of the engine
and frame to m, and back to the battery. The current may
flow in the opposite direction if the battery is connected in
the reverse way. It is immaterial which way the current flows.
When the cam rotates in the direction of the arrow, it lifts
the spring / and rocks the arm g so that the contact point d
is brought against r, thus completing the circuit when the
switch n is closed. The elasticity of the spring / prevents
undue pressure between the contact points.

As the cam continues to rotate, the lobe of the cam passes
from under/, and the spring action of y, together with the
pull of the coil spring p, separates the contact points rapidly.
This rapid separation is conducive to the procuring of a hot
spark suitable for ignition, without burning the contacts as
much as when the separation is slow.

41. It is desirable that the time during which the con-
tacts are pressed together shall be as short as possible, in
order to prevent unnecessary demand for current from the
battery and possible heating and fusing of the contact points,
especially if the contact is not good, as is often the case.

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§7

The igniter is generally made adjustable by hand with
regard to the time at which the spark is made in relation to
the position of the piston of the engine. Such adjustment
can be made by varying the distance between the igniter
spindle h and cam-shaft /, Fig. 24. By decreasing this dis-
tance, the spark will be retarded so as to come later in the
movement of the engine piston; by increasing the distance,
the spark will be advanced, or made earlier.

HIGH-TENSION IGNITION

42. Jump-Spark System. — With the Jump-spark, or
Mg^h-tension, system of ignition, the primary current is
converted by an induction coil into a secondary current of
sufficiently high tension to cause a spark to jump an air gap.

Pio. 26

With this system, a revolving contact timer is employed in
place of the snap cam k. Fig. 24. As there are no other
moving parts, the whole apparatus is extremely simple.

43. A sing:le-spark, hig^h-teusiou ignition system

with battery-current supply and non-vibrator, or transformer,
coil, is illustrated diagrammatically in Fig. 25. One end of
the secondary winding a is connected to one end of the

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§7 ELECTRIC IGNITION 37

primary winding b at ps, which may be called the primary-
secondary terminal of the transformer. This arrangement
reduces the number of connecting wires necessary for join-
ing the different pieces of apparatus together. The free end
of the primary wire at p may be called the primary terminal
of the transformer. The free end of the secondary wire at s
is the secondary terminal of the transformer. The primary
terminal p is connected through the hand switch h to one of
the terminals of the battery A. The other terminal of the
battery is connected to the frame of the automobile at d and
thus grounded. In the timer T, the stationary contact
piece k is supported by the insulating part /, and r is a
rotary part, or rotor, which is also grounded, being elec-
trically connected to the frame of the automobile. The
primary-secondary terminal ^5 is connected to the insulated
contact piece k of the timer. One side of the condenser c is
connected to the primary-secondary terminal ps, and the
other side is grounded by a connection to the frame of the
automobile at e. The secondary terminal s is connected to
the insulated electrode j of a spark plug /, and the other
electrode m of the plug is grounded through the engine and
frame of the automobile. The spark gap is between the
points of j and m, the safety spark gap being located at g.
The hand switch h is used to open the primary circuit and
thus stop the operation of the ignition apparatus. The
dotted lines indicate the grounded return circuit through
metallic parts of the frame, engine, etc. of the automobile.

44. When the primary circuit is closed by the timer as
the end of the rotor r comes into contact with the stationary
contact piece k, current^ will flow from the battery Ay
through the closed switch h, to the primary terminal/, then
through the primary coil to the terminal ps, then through
the timer 7" to the frame of the automobile, and finally to the
battery through the connection at d between the frame and
battery. •

At the instant of the breaking of the primary circuit and
the jumping of the spark at the spark plug, the high-tension

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38 ELECTRIC IGNITION §7

current flows (assuming a direotion of flow and taking the
spark plug as the starting point) from the insulated part /
of the plug to the secondary terminal s of the transformer,
through the secondary coil of the transformer to the primary-
secondary terminal/^, then through the primary terminal^,
through k to the battery, and through the battery to the
frame that carries it to the frame-connected, or grounded,
side m of the plug /; by then jumping the spark gap, the
current is again at the assumed starting pointy.

When the primary circuit is closed, there are two paths
that the secondary current may follow between the side m of
the spark plug and the primary-secondary terminal ^^. One
path is by way of the frame to the timer and thence through
k and the connecting wire to ps, and the other is from m
through the frame to </, then to and through the battery A
and the switch A to the primary terminal ^, and then through
the primary coil to^^.

43. In the scheme shown in Fig. 25, the only connecting
wire that requires insulation to resist high electric tension
is the one between the spark plug / and the secondary
terminal s of the transformer. The switch, battery, and
timer may be located anywhere in the primary circuit, so
long as the condenser is connected directly across the break
made by the timer. If the condenser is separate from the
coil, many arrangements of the parts can be made. The
condenser and the induction coil, however, are generally
placed together inside a box. So far as electrical conditions
are concerned, the condenser is connected to the two sides k
and r of the timer. While one part of the timer T is gener-
ally referred to as being stationary, it is usually made
movable through an eighth of a revolution or so, correspond-
ing to an arc of about 45°. This is done so that the timer can
be rocked by hand, in order to make the spark come earlier
or later in the rotation of the rotor r; that is, to advance or
retard the spark relative to the motion of the engine piston.
The rocking portion comprises the insulation / and the
contact piece ky which are rigidly connected together.

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ELECTRIC IGNITION

A timer whose contacts snap apart by spring action is
sometimes used in connection with a single-spark trans-
former, as stated in Arts. 17, 18, and 19.

46. A jump-spark ignition system with vibrator coil
and two batteries, as applied to a single-cylinder motor, is
conventionally illustrated in Fig. 26. At A and B are shown
the two batteries; at Cy the case enclosing the induction coil
and condenser, and on which the coil terminals and vibrator,
or interrupter, are mounted; at hy a hand-operated switch

Fig. 26

interposed in the connections between the batteries and coil;
at /, the spark plug; and at T, the timer.

In the position of the switch blade shown, battery A is in
circuit and battery B is idle. When the switch blade is
moved over to the right, A is cut out and B is put into cir-
cuit. In the mid-position of the switch blade, both batteries
are put in parallel. Both batteries are cut out by moving
the blade either to the extreme right or to the extreme left.
The secondary terminal s of the coil is connected to the
insulated part of the spark plug /. The batteries are con-
nected to one of the two remaining terminals of the coil.

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§7

and the timer to the other. These two terminals are some-
times marked for battery and timer, but in case they are not,
the operation of the coil will generally be practically as
satisfactory when the battery is connected to the one
terminal as to the other. The dotted line indicates the
grounded circuit, or frame connection. Either the positive
or the negative terminals of the batteries may be connected
to the frame. The switch, timer, and batteries may be
placed anywhere in the primary circuit.

Fio. 27

47. In Fig. 27 is shown a jump-spark ignition system in
which provision is made for obtaining a spark, even if the
vibrator for interrupting the primary circuit fails to operate.
Such failure may be due to fusing of the contact points at the
vibrator so that they are not separated by the action of
the magnet, or the speed of the motor may be so high that
the primary circuit is not closed long enough by the timer
to allow the magnet to draw the vibrator away from contact
with the screw pressing against it. This result is obtained

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§7

ELECTRIC IGNITION

by adding another condenser to the arrangement shown in
Fig. 26.

In Fig. 27, the parts above T and h represent the ordinary
induction coil with a magnetically operated vibrator v for
interrupting the circuit. At p is shown the primary terminal;
at Sy the secondary terminal; dX ps, the primary-secondary
terminal of the coil; and at c v, the usual condenser connected
across the contact points of the vibrator. The two sides of
the additional condenser ct are connected respectively to
the contact piece and the rotor of the timer 7". The batteries

Pig. 28

A and B, the hand switch h^ and the spark plug / are con-
nected in as usual. The safety spark gap is shown at g.

If the primary circuit is not broken at the vibrator, but
only at the timer, then the condenser ct acts in the same
manner as in the transformer system described in Arts. 43
and 44, and a spark passes at the spark plug. If the
vibrator is operating, but happens to be in position to close
the circuit at the instant it is opened at the timer, then
the condenser ^/ at the timer acts to break down the
arc in the timer and to produce a good spark at the spark

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ELECTRIC IGNITION

§7

plug. The condenser also acts to prevent fusing of the
timer contacts.

48. The auxiliary condenser f /, Fig. 27, can be elimi-
nated and the same effects obtained by grounding the con-
denser; that is, by connecting one side of the regular coil
condenser to the frame of the automobile and the other
side to the vibrator, as shown in Fig. 28. The condenser is
thus placed between the primary winding of the coil on one
side and the points of the vibrator and timer on the other,
so that the condenser may be said to be in parallel with the
vibrator and timer.

Pio. 29

49. Two Spark Pluj^s With One Coll. — By using an
induction coil with four terminals, jump sparks can be pro-
duced at two spark plugs at the same instant. Fig. 29
shows an arrangement of apparatus for this purpose. At A
and B are shown duplicate batteries; at h, the switch; at 7",
the timer; at p and p^, the primary terminals of the coil;
at s and s!, the secondary terminals of the coil; and at i and /',
a pair of spark plugs connected in series with the secondary
winding of the induction coil.

Assuming a direction of flow, the high-tension current goes
from the terminal s to the insulated part j of the plug /,

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§7

ELECTRIC IGNITION

jumps the gap to tn^ which is connected to the metal of the
engine, passes through the engine to m!, jumps to/', which
is insulated, and then passes to the other secondary terminal s! ,
If one of the spark plugs becomes fouled or injured, so that
the current passes through it without jumping the gap, the
other plug will operate nearly the same as usual if it is still
in good order.

50. Two-Cyllnder-Eiiglne Ignition. — The jump-
spark ignition system described in Art. 49 can be applied to
^

4 4 4 4^

Fig. 30

a two-cylinder, four-cycle engine in which the explosions
are to occvu: at equal intervals of time. One of the spark
plugs is placed in each cylinder. -The metal of the engine
furnishes the path for the current or circuit between their
uninsulated parts.

The spark occurs in each cylinder twice as often as it
is needed — once at the proper time for igniting the charge,
and once at about the completion of the exhaust stroke of
the piston. The latter spark has no effect when occurring

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44 ELECTRIC IGNITION §7

at this time, but under some conditions of the setting of the
timer, it may come after the fresh charge begins to enter the
cylinder. In such a case, the charge is liable to be ignited
at the wrong instant.

If the rotor of the timer turns at the same speed as the
crank-shaft, only one stationary contact is necessary for the
four-cycle, two-cylinder engine; if it turns at one-half the speed
of the crank-shaft, two contacts, half a revolution apart, are
necessary. The two contact pieces of the timer should be
electrically connected together. This method of ignition is
seldom used.

The other methods of ignition for two-cylinder motors are
practically the same as for engines that have more than two
cylinders.

51. Four-Cylinder Jump-Spark Ig^nltlon Wltli Bat-
teries. — The arrangement of an Indlvldual-colly Jump-
spark Ignition system for a four-cylinder engine is shown
in Fig. 30. It differs from an arrangement for a single-
cylinder engine only in the multiplication of spark plugs, of
induction coils, and of the insulated contact pieces in the
timer T, One of each of these parts is supplied for each of
the cylinders. Either battery A or battery B is connected
through the switch h to similar primary terminals of all the
spark coils c, so that the primary coils are in parallel. The
other primary terminals are connected one to each contact
piece of the timer.

As will be noted, the drawing shows that the wires lead-
ing to the timer contacts S and 4 are crossed, but they are
not in contact at the crossing. This is done so that, if the
rotor of the timer revolves left-handed, or counter-clockwise,
the sparks will be made in the cylinders in the order i, 2, 4, 5,
to accord with the requirements of an engine whose pistons
in the end cylinders move in unison and in the opposite direc-
tion to that of the pistons of the two middle cylinders, which
pistons also move in unison with each other. A timer of
the kind here used, with four insulated contact pieces, is
called a four-point tinier.

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ELECTRIC IGNITION

In order to keep the coils in operation in case the contacts
of the vibrator stick together, auxiliary condensers, one for
each spark coil, can be connected in as shown in Fig. 27; or,
the condensers in the coil boxes can be made to act across
both the timer and the vibrator contacts by grounding one
side of each condenser, as explained in Art. 48.

A six-cylinder ignition system of the same nature as that
shown in Fig. 30 may be obtained by further multiplication
of the spark coils and timer contacts.

DUAL IGNITION

52. Ijow-Tenslon Systems. — The wiring for one set
of dry cells and a generator in a low-tension ignition system
is shown in Fig. 31. When the battery is in use and con-

€

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HiHiH

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Pio. 81

tact between the insulated and uninsulated electrodes of the
igniter is made, current passes from the battery a through one
blade of the switch b to the insulated electrode of the igniter d,
then through the uninsulated electrode of the igniter to the
grounded connection e,\.o the coil Cy and back to the battery
through the other blade of the switch b. The kick coil c is
located between the frame connection, or ground, and the
switch b. In this position, the coil will be in circuit with a set
of batteries substituted for the generator / and connected
to the same switch wires as now lead to the generator.

222—14

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ELECTRIC IGNITION

§7

53. Fig. 32 shows double wiring throughout for a four-
cylinder engine with low-tension ignition, the same reference
letters as are used in Fig. 31 being applied to similar parts
in Fig. 32. The system is so connected up that either pair
of cylinders can be operated by a generator / or by either of
two sets of batteries a; or, all the cylinders may be operated

(

Fig. 32

by both sets of batteries acting together in case the batteries
become weak. A kick coil is generally not required in
circuit with a generator on a low-tension system, the induct-
ive action of the generator armature being sufficient to
replace that of a kick coil in a battery circuit.

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ELECTRIC IGNITION

(PART 3)

DIRECT-CURRENT GENERATORS

PRLNCIPIiBS or OPERATION

CLASSIFICATION OF IGNITION GENERATORS

1 . The electric generators commonly employed for ignition
purposes are divided into two principal classes, namely, those
which generate a continuous, or direct, current, and those
which generate an alternating current. The former are
known as direct-current generators, dynamo-electric generators,
or simply dynamos. The latter are known as magneto-electric
generators, or simply magnetos. There are two classes of
magnetos, (1) those which generate a low- tension current for
the make-and-break type of ignition system and for delivery
to both vibrator and non-vibrator induction coils, by which
the low-tension primary current is transformed into a high-
tension current, which is led to the spark plugs by the heavily
instilated secondary wiring, and (2), those which generate
a high-tension current, embodying within themselves all the
elements necessary to the production and distribution of such
current, thereby making the use of induction coils unneces-
sary. To avoid confusion in classifying magnetos, those
which deliver a low-tension current to a step-up coil, there
to be transformed into a high-tension current, might be called
coil-type magnetos. Some magnetos of this class are driven

eOPTIUOMTBD BY INTERNATIONAL TEXTBOOK COMPANY. ENTERED AT STATIONER*' HALL. LONDON

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2 ELECTRIC IGNITION § 8

by means of belts or by pulleys pressing against the flywheel;
others are driven in synchronism with the crank-shaft by
means of gears whose positions have a fixed relation to the
point of maximum current production at which the spark
takes place. To distinguish the belt-driven types from the
gear-driven types of magneto, the former may be called
non-synchronous magnetos.

ELEMENTARY DIRECT-CURRENT GENERATOR

2. Whenever the number of lines of force enclosed by a
coiled conductor is changed, an electromotive force is induced

in the coil. If a conductor in
the form of a closed loop, or
coil, is moved in the direction
of the arrows a or fc, Fig. 1,
between the poles N and S
of a horseshoe magnet, lines of
force will be cut by the coil,
and the electromotive force
^°- ^ thereby induced will cause a

current to flow around the coil. The arrows along the sides
of the loop indicate the direction of the current when the
motion is in the direction of the small arrow a. Some mechan-
ical force is required to make the conductor cut through
the magnetic field.

3. The direction of the induced electromotive force in a
conductor is the same as the direction in which this force
would cause a current to flow if the conductor were made a
part of a closed circuit. When a conductor is moved across
a magnetic field, the induced electromotive force will act in
a direction depending on the direction of the lines of force
and the direction in which the conductor is moved. The
following rule applies:

Rule. — Place the thumb, the forefinger, and the middle finger
of the right hand each at right angles to the other two; if the
forefinger shows the direction of the lines of force and the thumb

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§ 8 ELECTRIC IGNITION 3

shows the direction of motion of conductor, the middle finger
will show the direction of the induced electromotive force or the
resulting current (see Fig. 2).

By always keeping the three fingers at right angles to one
another, this rule may be applied to determine the direction
of an induced current in any case in which the lines of force
and the direction of motion of a conductor are at right angles
to each other; for the hand as a whole may be placed in any
position that may be necessary to make the forefinger and the
thumb point in the proper directions. For example, in Fig. 1,
if the forefinger points in the direction indicated by the small
arrowheads on the dotted lines representing the flow, or flux,
of magnetism from the north to the south pole, and the thumb
points in the direction indicated
by the arrow a, the middle finger
will point in the direction of the
induced current, the rule apply-
ing only to the conductor that is
actually cutting the magnetism
and not to the other sides of the
loop.

The intensity of the electromotive
force depends on the rate at which the conductor cuts across
the lines of force ; that is, on the niunber of lines of force cut
per second.

4. Essential Parts of an Electric Generator.
The simplest of all mechanical motions is that of rotation, and
electric generators always use this principle for sweeping the
conductors through the magnetic field. There are essentially
two parts to such a machine: the -field magnet, wherein is pro-
duced the necessary magnetism ; and the armature, on or near
whose surface the working conductors (those which cut the
lines of force) are arranged. These two parts are rotated
relatively to each other, it being immaterial, except for con-
venience, which is stationary and which is rotated.

5. A single conductor can seldom be made to generate a
desired voltage, so that on an armature a number of con-

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4 ELECTRIC IGNITION § 8

ductors are usiially connected up in series and in parallel, in
the same way as electric batteries, until the required voltage
and current-carrying capacity are obtained.

6» Action of Armature. — The direct-current genera-
tors used for ignition purposes generally have armatures
whose magnetic cores are in the form of a cylinder that is
either smooth or grooved lengthwise. Such an armature is
known as a drum armature. It is convenient to consider
first the nature of the current generated in an elementary
form of drum armature with a single closed coil, and then
the method of causing the current from a similar coil to flow
in only one direction through the portion of the circuit
external to the armature.

An elementary drum armature with a single closed coil is
shown in Fig. 3 between the pole pieces a and b of the magnetic

field. The armature core c
is cylindrical in form;
the end view is shown.
The straight parts d and
e of the coil lie along the
cylindrical surface of the
I drum and are perpendic-
^'G. 3 iiiar to the plane of the

paper on which the figure is printed. When the drum
is rotating counter-clockwise, as indicated by the feathered
arrow just beneath it, and the coil is passing through
the position shown, the straight parts d and e of the coil are
cutting through the magnetic lines of force. This induces
an electromotive force and causes an electric current to flow
through the wire of the coil in the direction indicated by the
two full arrows on the front of the coil and by the dotted arrow
on the back end. The current flows in this direction during
the time the part d is cutting through the lines from 1 to 2,
and the part e from 3 to 4- The current flows through the
front of the coil in the direction from the north pole to the
south pole. While d is moving from 2 to 3 and e from 4 to i,
no magnetic lines of force are cut; consequently, no current

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ELECTRIC IGNITION

Pig. 4

flows through the coil. As d continues to move from S to 4
it cuts through the same lines and in the same direction that e
did before; at the same
time e cuts through the
lines previously cut by d
and in the same direction
as d cut them. There-
fore, when e is passing
through the position
shown in Fig. 4, the elec-
tric current will flow through the front of the coil from
e to d, as indicated by the full arrows. The direction
of flow through the front of the coil is from the north pole
toward the south pole, as before, but, inasmuch as the sides
d and e of the coil have interchanged positions, the current
flows through the wire in a direction opposite that which it
first had. An alternating current is induced in the coil by
its rotation in the magnetic field, as described.

7. The alternating current in this elementary armature
reverses its direction of flow twice during each revolution.
The reversals of current occur while the coil is passing through
its positions perpendicular to the general direction of the

magnetic flux. In
these two positions
all the magnetic lines
pass through the coil,
but it is cutting none
of them by its mo-
tion. In one of these
positions the straight
part d of the coil lies
between 1 and 4 and
the other straight
part e lies between S
and 3. These are the
two neutral positions of the coil, in which it is electrically
inactive while the annature is rotating.

Fig. 6

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ELECTRIC IGNITION

§8

8. In Fig. 5 is shown a simple form of direct-current
generator having an armature on which there is a single turn
of wire terminating iil a ring split into two parts, approxi-
mately half rings, on which the stationary brushes e, f slide as
the ring rotates. The split ring is the commutaior. The
half rings, or segments, are insulated from each other and
from the shaft. The brushes are so placed that, at the instant
when the coil passes through its neutral, inactive position and
the electromotive force in it reverses, the segments each break
contact with one brush and slide under the other. The elec-
tromotive force generated in the conductor passing xmder the
north pole when the core and the coil are rotating counter-
clockwise, as shown by the arrow, is always toward the seg-
ment imder the brush ^; hence, the current leaves the armature
by way of brush e, which is therefore marked +, passes

Pio. 6

through the external circuit /?, and returns by way of brush /,
which is therefore marked — .

The current through the external circuit, instead of flowing
alternately in opposite directions, flows in one direction only,
but is in impulses, or pulsations, and may be represented by
the full-line curve in Fig. 6.

By evenly spacing a number of coils on the armature core
and connecting them to a commutator having the proper
number of segments, two coil ends to each segment, the
electric impulses can be made to so overlap each other that a
smooth, or continuous, direct current is obtained in the
external circuit.

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ELECTRIC IGNITION

DETAIIiS OF CONSTRUCTION

ARMATURE AND COMMUTATOR

9. In a solid-iron armature core rotating in a magnetic
field, there are set up in the iron of the core electromotive
forces that cause local currents, or eddy currents, to flow.

Fig. 7

Fig. 8

Fig. 7 shows how these currents circulate. The lower half
of a solid iron core is shown at C. When the core rotates,
eddy currents flow in the iron, as shown by the lines and the
arrowheads on the section. These currents cause the core
to heat, and they serve no good purpose. To prevent them,
armature cores are usually laminated , as shown in Figs. 8
and 9 (a) ; that is, they are built up of disks of the proper size
punched from sheet iron.

(a)

Fig. 9

10. Fig. 9 (a) shows an armature core A for a small
ignition dynamo, and (b) shows one of the laminations, or
disks, of which the core is made. The laminations are
punched from soft sheet iron with a suitable die, so that,

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8 ELECTRIC IGNITION § 8

when assembled in the core, the slots a are formed. On the
inside of each disk is a shoulder b that slips into a notch in
the brass sleeve on which the disks are assembled. The disks
are compressed by hydraulic pressure and clamped together,
and the sleeve with the complete core is then slipped over
the shaft and keyed tightly to it.

The commutator B consists of copper segments c insulated
from each other by thin sheets, or bodies^ of mica d, or a com-
position of mica and shellac called micanite; they are also
insulated from the shaft or sleeve on which the commutator
is assembled by cylinders or cones of the same composition.
The commutator also is securely keyed to the shaft.

11. The armature-core slots are insulated with suitable
paper or cloth insulation, and insulated wire is woimd in the

Fio. 10

slots — a certain number of turns in each coil, the number
depending on the voltage desired and on the speed at which
the dynamo is to run. The core and commutator shown in
Fig. 9 are designed for twelve armature coils. Fig. 10 shows
one of these armatures completely wound. This form of
armature reduces the air gap between the armature and poles
of the magnetic field. The magnetic flux is consequently
greater, and the wires cut through a stronger magnetic field
than when they are wound on a smooth core.

12. The wires leading from the armature coil to the com-
mutator segments can be connected to the segments in such
a manner as to bring the brushes in any desired position, the
only limitation being that the brushes must be diametrically
opposite each other in a bipolar (two-pole) machine. This
is accomplished by bringing the ends of the neutral coil or
coils to the segments where the brushes are to make contact.

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§8

ELECTRIC IGNITION

Flo. 11

FIEIiB MAGNETS AND COILS

13. If a current of electricity flows through a wire wound
around the straight portions of a U-shaped bar of soft iron,
as indicated in Fig. 11, the ends
of the bar will become the
north and south poles of the
magnet. The relative directions
of winding the two coils are the
same as if the winding had
been continued along the bar
over the curve, or yoke, from
one coil to the other. By
providing suitable pole pieces at
the ends of an electromagnet
of this form, it can be used for
producing the magnetic field of
an electric generator.

14. A more compact form of field magnet is obtained by
the construction shown in Fig. 12. In this design, the magnet
poles are projections from a circular piece, instead of the ends
of a U-shaped core of the form just described. The winding

on both pole pieces is in
the same direction, so
that the poles are made
north and south. The
magnetic flux divides
equally through the two
halves of the ring, as
indicated by the feath-
ered arrows.

1 5 . Instead of using

an electromagnet, in

which part of the cur-

P»G- 12 rent that is delivered by

the armature is utilized for magnetizing the core of the

magnet, permanent magnets may be employed, as

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ELECTRIC IGNITION

§8

shown in Fig. 13, for producing the field in which the
armature of the direct-current magneto-electric generator
rotates. The armature is wound so that the brushes make
contact at, or near, the top and the bottom segments of the
commutator, to which the inactive coils are always con-
nected in this arrangement. When the armature is rotating,
the current flows continuously as a direct current from the
positive (-f ) brush out through the external circuit R and
back to the negative ( — ) brush.

16. In an electromagnet, the strength of the magrnetl-
zing force, or magrnetomotive force (abbreviated to M. F.),
by which the lines of force are produced, is proportional to the
strength of the current flowing through the field coil, or mag-
netizing coil, and to the number of com-
plete turns through which the current
flows. The product of the current, in
amperes, and the number of turns in the
field coil gives the magnetizing force, in
ampere-turns. A current of 10 amperes
flowing through a field coil of 20 turns

jj^ gives exactly the same magnetizing force
as 1 ampere through 200 turns; or 200
Fig. 13 ampere-tums in each case.

17. When the number of ampere-tums on an electro-
magnet is increased, the number of lines of force, or the
magnetism, through the magnet, is increased, but not in direct
proportion. When there are few lines of force through a mag-
net, a little increase in the magnetizing force will produce a
considerable increase in magnetism; but, if the magnetizing
force is increased sufficiently, a point will be reached where
but very little further increase of magnetism can be obtained.
The magnet core is then nearly filled, or saturated, with mag-
netism. Complete saturation is never reached, but there is
a limit beyond which it is impracticable to increase the magnet-
izing force further; dynamo-electric generator field magnets
are generally run at considerably below magnetic saturation.

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§8

ELECTRIC IGNITION

18» Dynamo-electric generator fields may be separately
excited or self-excited, according as the exciting current is
obtained from a separate source or from the dynamo itself.
There are several methods of using current from a direct-
current generator to magnetize, or excite, its own field
magnets. Self-excited dynamo-electric generators
may be series-wound, shunt-wound, or compound-wound. In
a serles-'wound electric generator, the current that
leaves the positive brush flows through the external circuit
and then through the field coil before returning to the nega-
tive, brush. The field winding is thus in series with the
external circuit — hence the name series-winding. If the cur-
rent through the external cir-
cuit, or the load, is increased
by an increase in the speed of
rotation of the engine by
which the armature is driven,
the current through the
series field winding must like-
wise increase, thus increasing
the magnetizing force and
consequently the number of
lines of force. The greater
the number of lines of force
cut by the armature coils, the
greater is the electromotive
force generated; hence, the greater the load on a series-
wound generator, within the limits of its capacity, the
greater is tha electromotive force it will generate. Since
an increase in the speed of rotation of the armature
increases the load and consequently the electromotive force,
series-wound generators are not used for ignition purposes on
automobiles, because it is desirable to maintain as uniform a
voltage as possible with wide variations of engine speed.

PlQ. 14

19. The method of field excitation that probably finds
most application to direct-current ignition generators is shown
in Fig. 14, which illustrates the connections for a sliunt-

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12 ELECTRIC IGNITION § 8

wound dynamo-electric generator. The field magnet
is wound with an exciting coil whose ends are connected to
the brush terminals -f B and —B. The external circuit R is,
of course, connected to the brush terminals. The field coil
thus forms a shunt, or by-path, for part of the current deliv-
ered by the armature. The field coil consists of a great num-
ber of turns of small insulated wire. The resistance of the
field coil is great enough to prevent a flow through it of more
than a small proportion of the amount of current that the
generator is designed to supply.

When the external circuit R is closed, as shown, current
flows through both the external circuit and the field coil.
The amount of current flowing through each circuit is inversely
proportional to the electric resistances of the circuits. The
amoimt of current flowing through the armature is the sum
of the amounts in field and external circuits. If the external
circuit R is broken and its current stopped, the current
through the field coil will continue to flow as before.

When the armature stops rotating, the current through
the field coil also stops, and the field loses most of its mag-
netism. There is remaining, however, sufficient residual
magnetism to induce enough electromotive force in the
armature to cause the generator to "pick up" and furnish
current in the usual manner.

As the speed of rotation of the armature of a shunt-wound
generator increases, the electromotive force at the terminals of
the generator becomes less ; this makes the field current or mag-
netizing force less, thus causing a decrease of magnetism and
a further decrease of voltage. This peculiarity makes a shunt-
wound generator very sensitive to changes of speed. How-
ever, by proportioning the field windings so that the magnet
cores will be very highly saturated, a slight change of field cur-
rent will produce but little change in the number of lines of
force, and the change of voltage with slight changes of speed
will therefore be small.

20, A compound field winding is a combination of a
series and a shunt winding. The series-winding usually con-

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§8

ELECTRIC IGNITION

sists of only a few turns, the larger part of the magnetomotive
force being furnished by the shunt winding. An increased
speed of rotation of the armature of a series-wound generator
usually causes the machine to generate increased electromo-
tive force; a similar increase of speed with a shunt- wound
generator usually causes it to generate decreased electromo-
tive force. Consequently, by combining the two kinds of
winding and properly proportioning them, a generator can be
made to generate almost a constant electromotive force, even
though the speed may change considerably.

21. The intensity of the electromotive force generated by
a dynamo-electric generator depends, first, on the number of

Pio. 15

coils on the armature and the number of turns of wire per coil,
that is, on the total number of armature turns; second, on the
intensity of the magnetic field; and, third, on the speed at
which the armature is rotated. Increasing any one of these
three quantities, the others being unchanged, increases the
voltage of the generator.

22. A self-excited direct-current generator constructed on
the principles mentioned in Art. 18 is illustrated in Fig. 15,
which shows the complete ignition dynamo with part of the

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ELECTRIC IGNITION

§8

field frame cut away so as to show the various parts of the
machine in place. The armature rotates between the poles a,
each of which has an exciting coil b, A brass ring c, fitted
into the body of the machine, supports the brackets that carry

Fig. 16

the commutator bearing and the brush holders. This ring
with the brackets, bearing, brush holders, and carbon brushes
is shown in Fig. 16. The brushes d, which in this case are
blocks of carbon or graphite, are shown removed from the
holders ; when in place they are held against the commutator
by springs d\ The brushes stand radially, to allow the
armature to rotate in either direction without injury to the

brushes. Conducting wires connected to the binding posts e,
which are in electrical contact with the brushes, convey the
current to the external circuit.

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§ 8 ELECTRIC IGNITION 15

23. The pole pieces are removable, and are held in place
by screws /, Fig. 15, through the frame. Fig. 17 shows the
pole pieces and field coils removed from the frame. After
the coils are woimd and insulated with wrappings of tape,
etc., they are placed on the poles before the latter are put
into the generator. It can be seen that the poles are con-
siderably broadened at the end next to the armature.

24. The generator shown in Fig. 15 is driven by a cone-
shaped friction wheel g that bears against the rim of the
flywheel. The axis of the armature is set at an angle with
the flywheel. Governor arms carr)dng the weights h are
attached by two pins to a split ring fastened to the armature
shaft. Bearing against this split ring is a coiled compression
spring i that forces the friction wheel g against the flywheel.
The centrifugal force of the rotating governor weights h is
transmitted to the flange of the friction wheel g by means of
the links shown, pulling the friction wheel back against the
influence of the compression spring and reducing the pressure
of the friction wheel against the fljrwheel.

When the speed of the armature reaches a predetermined
maximum value, the reduction of pressure thus caused
between the friction surfaces becomes sufficient to allow the
friction wheel to slip on the flywheel. The armature speed
is thus maintained nearly constant as long as the fl)rwheel
rotates as fast as, or faster than, is necessary to drive the
armature at the required speed. The diameter of the friction
wheel is made small enough to give the armature its maxi-
mum speed when the flywheel is rotating much slower than
the speed of an engine running by its own impulses. There
is consequently continuous slipping between the pulley and
flywheel when the engine is running.

A direct-current generator of this form for ignition use
generally is designed to give a pressure up to 10 volts, or
Somewhat more, and from 10 to 12 amperes of current. For
automobiles, a direct-current generator gives its best service
when used in conjunction with a storage battery.

222—15

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ELECTRIC IGNITION

§8

METHOD OF IKSTALIiATION

DIRECT-CURRBNT GENERATOR AND STORAGE BATTERY

25. Storagre Battery **Ploated on tlie Lilne." — A

direct-current generator and a storage battery, arranged to
operate in conjunction by the method known as *' floating
the battery on the line," are shown diagrammatically in

Fio. 18

Fig. 18. In this illustration, the generator is shown at a;
the storage battery, at 6; the induction coil, at c; the high-'
tension spark plug, at d; the timer, at e\ and a hand switch,
at /. In the system is included an automatic cut-out for
cutting out the armature of the generator from the main

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§ 8 ELECTRIC IGNITION 17

circuit in case the speed of the generator becomes so low that
its voltage drops considerably below that of the storage
battery. With another type of the generator, shown in
Fig. 15, the automatic cut-out is incorporated as a part of
the generator. The circuit-breaker arm g. Fig. 18, of the
cut-out has a contact point that makes contact with A, to
which one terminal of the winding of the electromagnet i
is connected. At ; is shown a compression spring that tends
to force the arm g away from the magnet and the contact
piece h.

When the apparatus is in operation and the generator is
producing a voltage higher than that of the storage battery,
the current from the positive (-f ) brush of the generator
flows to the cut-out magnet i and then divides. Part is
shunted through a small- wire winding of numerous turns on
the magnet, then through the field-magnet winding of the
generator, and back to the negative brush of the generator.
This shunt current magnetizes the core of the cut-out suffi-
ciently to draw the circuit-breaker arm g toward the core
against the resistance of the spring ;, thus bringing the con-
tact point on g against the contact piece h. The balance of
the current from the positive brush passes around the magnet i,
through a coarse-wire winding of few turns to the contact
piece A, then through g to fe, and out to the junction point /.

26. If the voltage produced by the generator at the
point / is just equal to that of the storage battery, then all
the current in the main line from the generator will pass
through / and the induction coil c, thence through the timer e
to the frame connection, and back to the negative brush of
the generator. Under this condition, no current flows
through the storage battery in either direction; it is neither
discharging nor being charged.

In case the speed of the generator increases so as to produce
a voltage at / higher than that of the storage battery, current
will also flow through the storage battery against its electro-
motive force, thus charging the battery. The direction of
current flow through the system under this condition is

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18 ELECTRIC IGNITION § 8

indicated on circuits by the arrowheads. The current flowing
in the direction thus indicated in the main circuit acts together
with the shunt current to strengthen the cut-out magnet and
maintain good contact at h.

On the other hand, if the generator slows down, so that its
voltage is less than that of the storage battery, it will not
deliver any current to the system. Under this condition,
the storage battery will furnish the current for the spark coil.
If the voltage of the generator falls considerably below that
of the storage battery 6, the latter will send current back
through the armature of the generator in the direction indi-
cated by the broken arrows alongside the lines of the circuit.
This current passes in the reverse direction from that indicated
through the coarse winding of the automatic cut-out, and
opposes the magnetizing effect of the fine-wire, or shimt, coil.
The cut-out magnet thus becomes weakened to such an
extent, before the reversed current becomes great enough to
injure the generator, that the expansive action of the spring ;
forces the circuit-breaker g back so as to break contact at h
and thus interrupt the main current. The generator is thus
protected against excessive current, which would be injurious
to its armature and commutator in case of slowing down or
stopping, and exhaustion of the battery is prevented.

27. When the speed of the generator again increases to
normal, the current sent through the shunt coil becomes great
enough to magnetize the core of the cut-out and draw the
arm g toward the magnet, thus again closing the main circuit
and reestablishing the normal condition of operation.

The speed of the generator can be adjusted by moving it
relatively to the flywheel against which the friction wheel
presses. By thus regulating the speed of the generator so
that its voltage is about that of the battery when fully charged,
current will be delivered to keep it always well charged after
the generator has been running for some time. The voltage
of the system is practically that of the battery.

The advantage of this system is that a constant electric
pressure is always at hand. This is a convenient feature for

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§ 8 ELECTRIC IGNITION 19

starting the engine and can also be utilized for electric
lighting. The lights on the vehicle can be kept burning
whether the engine is running or not. The length of time
that the lights can be burned when the generator is not
running depends, of course, on the current required for them
and on the capacity of the battery.

MAGNBTO-BLBCTRIC GENERATORS

PMNCIPIiBS OF OPERATION

THEORY OF THE MAGNETO GENERATOR

28. Jjb;w Of Electromaisrnetic Induction. — ^The action
of the magneto generator depends directly on a law of elec-
tromagnetic induction. One way of stating this law is, that
if the number of lines of force passing through a coil of wire
is varied, an electromotive force will be set up in the coil,
the intensity of which will depend on the rate at which the
lines are varied, and the direction of which will depend on
the direction of the lines and whether their number is being
increased or diminished. One way of varying the number
of lines through a coil is to pass a variable current through
another coil wound on the same core, as in an ordinary induc-
tion coil. Any changes in the strength of the current in the
primary winding cause corresponding changes in the strength
of the magnetic field, which, by the law just stated, produce
electromotive forces in the secondary coil. Another way of
changing the number of lines of force passing through a coil
is to move an electromagnet or a permanent magnet in the
vicinity of the coil. Still another way is to move the coil
with respect to the magnet; and it is by this method that the
magneto generator is made to produce electromotive forces,
and, therefore, when the circuit is closed, corresponding
currents.

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§8

29. Induction In Bevolving: Lioop. — In Fig. 19 is
shown a closed loop of wire that may be revolved about a
horizontal axis x x within the field of a set of three permanent
magnets N, S. The lines of force are indicated by the hori-
zontal arrows, their direction being from the north pole to
the south pole according to the usual conception of their flow.
The rotation of the loop about the axis :«: ^ in the drection of
the curved arrow may be given by any suitable means.

When the loop is in its horizontal position, it will lie in a
plane parallel to the lines of force, and therefore will include

none of the lines.
As it is turned into
the position shown
by the full lines, it
will include more
and more of the lines
of force, and there-
fore .will have an
electromotive force
and a corresponding
current set up in it
in the direction of the
arrows a. When the
coil reaches its verti-
cal position, it will
P^o- 1® include all the lines

of force, and, from that point on, the number of lines through
the coil will be in the same direction, but will be decreasing.
Therefore, the direction of the current through the coil will
change after passing the vertical position, and the flow of cur-
rent will then be indicated by the direction of the arrows b.

30. If the coil is revolving at a constant speed, the rate
of change of the lines of force through the coil will be very
slow as it approaches and recedes from its vertical position,
being zero when the plane of the coil is at right angles to the
direction of the lines of force, and therefore the induced
electromotive force here is zero. As the coil approaches its

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§8

ELECTRIC IGNITION

horizontal position, the rate at which the number of lines
through it is changing will increase, and the electromotive
force will therefore increase correspondingly, although the
actual number is more and more rapidly being reduced to
zero. When the coil reaches its horizontal position, the
electromotive force in it will be a maximum because the rate
of change of the lines of force is a maximum, although the
number threading through the coil is zero. At that point,
the number of lines passing through the coil again begins to
increase; this would produce a change in the direction of the
electromotive force were it not for the fact that the direction
of the lines through the coil relative to the plane of the coil
also changes. The electromotive force is therefore at a
maximum at the horizontal position of the coil, because the

Fio. 20

rate of change of the lines through the coil at that point is a
maximum. As the coil again approaches its vertical position,
the rate of change becomes less and less, and as it reaches
that position, no change takes place, and the electromotive
force therefore becomes zero. From this point on to the
starting point, the number of lines decreases, therefore, again
producing an electromotive force in the opposite direction,
which becomes a maximum as the horizontal position is
reached.

31. Graphic Bepresentation of Magn^eto Current.

The flow of the. current to and fro in the coil may be repre-
sented by a curve, such as is shown in Fig. 20, the distances
above or below the horizontal axis a i being made proportional

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22 ELECTRIC IGNITION § 8

to the instantaneous values of the current or the electro-
motive force, whichever the curve is considered to represent.
Assuming the curve in Fig. 20 to be an electromotive force
curve, the point a on it corresponds to the vertical position
of the loop in Fig. 19. At this point no electromotive force
is set up in the loop, and therefore the point a is on the hori-
zontal axis of the curve. As the loop rotates on its axis, the
electromotive force gradually increases until it lies in a
horizontal plane, where the electromotive force is a maximum
because the lines of force are then being cut by the loop at a
maximum rate. This condition is represented by the point b
on the curve where the electromotive force is a maximvmi.
From the horizontal position of the loop in Fig. 19, the elec-
tromotive force remains in the same direction, but decreases
until the coil again reaches a vertical position, when it
becomes zero ; this is represented by the point c on the curve.
At this point, the direction of the electromotive force changes
and the curve passes below the horizontal line; and during
the next half revolution of the loop, while approaching the
second horizontal position, the changes are of the same
nature, but in an opposite direction, the electromotive force
reaching a maximum in this direction at the point d corre-
sponding to the second horizontal position of the loop, and
again decreasing to zero, as shown at e, when the loop is at
the same vertical position from which it started. A complete
revolution of the coil, therefore, produces one complete cycle
of changes in the electromotive force and in the current, as
represented by the curve ab c de, the curve efghi repre-
senting a second similar cycle of changes in the electromotive
force. While in this case the electric cycle is completed
during one revolution of the armature, some magnetos are
so constructed that the complete electric cycle is passed
through in less than one revolution of the armature.

32. The electromotive force generated in the coil is alter-
nating and if the coil is made a part of a plosed circuit an
alternating current will flow through the circuit. If the
electromotive force generated while the coil is passing under

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§ 8 ELECTRIC IGNITION 23

one pole is called positive, that generated while passing under
the other pole will be negative, and the loops of the curve in
Fig. 20 are made to indicate the change in direction by their
reversed position with reference to the zero line.

33, Current Frequency. — The frequency of an

alternating current is generally measured in the number of
its electric cycles per second. A rapidly alternating current
has high frequency; a slowly alternating current has low
frequency.

ELEMENTARY MAGNETO GENERATOR

34 • An elementary form of alternating-current magneto-
electric generator is illustrated in Fig. 21, which shows the
armature core and pole pieces N and S of permanent magnets

Fio. 21

to which they are attached, and also a coil consisting of two
active conductors c and d connected in series and having their
free ends joined to two metal collector rings, or slip rings,
g and h. As the armature core and the coil rotate, con-
ductor c is passing under a north pole at the same time that
conductor d is passing under a south pole, so that the elec-
tromotive forces generated in the two conductors, though
opposite in direction with reference to the poles, are the same

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24 ELECTRIC IGNITION § 8

in direction with reference to the coil; hence, the electro-
motive force between the collector rings is the stim of the
forces generated in conductors c and d. Stationary copper
strips e and /, called brushes, rub on the collector rings as they
rotate with the armature, and an alternating current flows
through the brushes and the external circuit R. The arrows
along the conductors and the external circuit show the direc-
tion of the current at the instant represented. When the
armature has rotated until the conductors c and d have
exchanged positions, the direction of the current through the
coil and the external circuit will be reversed.

35. Instead of having but a single turn of wire, as in the
loop shown in Fig. 21, a coil consisting of a great number of
turns is used in practice, so that the electromotive force
generated in each turn may be added to that of all the others.
Furthermore, in order that the greatest possible number of
lines of force may flow between the magnet poles and through
the coil, the coil is wound on a core of soft iron adapted to fit
closely between curved polar extensions, or pole pieces, of iron
secured to the poles of the permanent magnets.

DBTALLS OF CONSTRUCTION

ARMATURE CORE AND WINDING

36, The magneto-electric, or alternating-current, gene-
rators used for ignition purposes usually consist of an arma-
ture core a. Fig. 22, having wound thereon a single coil of many
turns of fine insulated wire, and arranged to rotate between
the poles b of one or more U-shaped permanent magnets iV, 5.
The armature core is usually made with a cross-section resem-
bling the letter H, as shown by the end view in Fig. 22 and
the perspective view in Fig. 23 (a), and may be solid iron or
laminated, the best ones being laminated. One end of the
armature coil is usually connected to the armature shaft,
or spindle, and the other to an insulated pin or ring. The

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ELECTRIC IGNITION

collecting brushes are arranged to rub against the shaft and
the instilated pin or ring, respectively. The shaft is some-
times nm directly through the core, but on some modem
magnetos the shaft is in two parts, each bolted to an end plate,
which is attached to end projections on the armature core,
leaving between the plate and the body of the core a space
for wire.

Fig. 23 (b) shows such a core completely woimd. The coil
is wound solid, as shown at 6 in the sectional end view,
Fig. 23 (c), instead of being separated into two parts, as
would be necessary if the shaft extended through.

Fig. 23 (c) also shows, by the dotted
lines, how the magnetic flux passes through
the core and the coil when in the position
shown. When the armature has ttimed
one-fourth revolution, so that the iron
projections c are opposite the neutral
spaces between the poles, almost no mag-
netism passes through the coil. As the
core rotates, it thus cuts the magnetism
in and out and generates an alternating
current.

37. In magneto generators for auto-
mobile use, the slip ring is frequently Pig. 22
eliminated by making the spindle hollow and carrying one
of the armature wires out through the hole to an
insulated contact piece at the end of the spindle. This
contact piece may be only an insulated pin against whose
ends the part substituted for the brush bears. In some
cases, the brush that would bear against the spindle is not
used, but the metallic contact between the spindle and its
bearings is depended on for making electric connection
between the spindle and the frame of the generator. This
arrangement is not always satisfactory, however, because the
film of oil between the spindle and its bearing is some-
times thick enough to act as an insulator and thus prevent
electric connection between them.

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ELECTRIC IGNITION

§8

38. In Fig. 23 (6), one end of the coil a is carried out
through the hollow spindle b to the insulated piece c, and the
other end is fastened to the core, or head-piece, by the screw d.
The sharp edges of the parts e and / throw off the oil as the
armature rotates and cause it to drip off when the armature

Fig. 23

is not rotating, so that the oil will not get into the armature
winding. In Fig. 23 (d), one end of the armature winding a
is connected to the insulated slip ring 6, and the other end is
connected to the armature core and spindle. The deep
flange c and the shallow flange d prevent oil from the bearings

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§ 8 ELECTRIC IGNITION 27

from reaching the winding, and the flange c also insulates the
slip ring h from the ball bearing. The end pieces e and / are
made of some non-magnetic material, generally brass, bronze,
or aluminum alloy, so that they will not form a magnetic
path between the magnetic poles and cause the mag-
netic flux to deviate from the desired path through
the core around which the coil is wound. The spindle
is usually made of steel. The non-magnetic heads magnetic-
ally insulate the spindles from the armature core. The cir-
cumferential bands h around the armature hold the wires of
the coil in place, so that they will not fly outwards when the
armature is rotating. They also are made of non-magnetic
material. Each armature shows at the left-hand end a spur
gear g by which it is driven. The bearings in Fig. 23 (6) are
of the plain cylindrical type,
with the spindle forming the
journal, which has sliding con-
tact with its bearings; the
armature shown in Fig. 23 (d),
however, has ball bearings.

39. When the armature
core is made of one solid piece ^'® 2"*

of wrought iron or soft steel, electric currents of considerable
magnitude are induced in it as it rotates between the magnet
poles. These currents flow from one part of the core to
another part, and on account of the nature of their flow are
called eddy currents. They are objectionable on account
of heating the armature and reducing the electric pressure
that is induced in the armature coil. In order to eliminate
the eddy currents as far as possible, the core is made up of
thin sheet-metal punchings or stampings, as shown in Fig. 24.
The metal sheets from which the pieces are punched or stamped
are about the thickness of thin stovepipe iron or even thinner.
Iron and steel of the softest and purest quality are used in the
best construction. The stampings are placed side by side to
build up the core. They are sometimes separated from each
other by thin sheets of paper, so as not to come into close

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ELECTRIC IGNITION

§8

metallic contact and thus form electric connection. In other
cases, only the black oxide of iron on the surface is depended
on to insulate the stampings from each other electrically.
The set of stampings is compressed together and fastened by
bolts and rivets.

40. Armature Winding:. — The electric pressure, or
voltage, of the elementary generator shown in Fig. 21 can
be doubled by giving the armature winding two turns around

the core instead of one, if the
two turns are in series. The
turns are in series when, in
winding the coil, the wire is
wrapped twice around the
core instead of once, and the
two ends are connected as
before. The series- winding is '
the same as wrapping a string
twice around a package. If
the number of turns in series
is increased still more, the volt-
age that the armature will
develop will be correspondingly
increased, provided all other
conditions remain the same
as before. In actual practice,
for this form of winding, the
voltage of the generator is nearly proportional to the number
of turns of winding on the armature core. An armature
wound as in Fig. 23 (b) and (d) is called a sliuttle-^wound
armature.

Fio. 26

FIELD MAGNETS

41. Fig. 25 shows the magnets, or field, used with arma-
tures of the form illustrated in Fig. 23 (6). ^ The field is made
up of three magnets placed side by side. Each magnet is
double, or compound, consisting of one magnet a fitted over
another b. Iron or soft-steel pole pieces c bored to suit the

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ELECTRIC IGNITION

armature are attached to the magnets. The magnets are
fastened firmly to a non-magnetic plate d that forms the base
of the generator. This base may be of brass, wood, vulcanized
wood fiber, or some other suitable material.

The thinner bar steel that can be used by making each
magnet in two component parts can be given a greater degree
of hardness than the thicker material that would be required
if each magnet were made in one piece. The harder the
material, the better it retains its magnetism. Also, the
thinner bar of hard steel is more easily magnetized than the
thicker bar. On the whole, a stronger magnetic field and
more permanent magnets are obtained by this method of
making up the field.

liOW-TENSION MAGNETOS

42. When a magneto generator delivers a current of low
voltage, such as is used for contact ignition or for the primary
winding of a spark coil, it is generally known as a low-ten-

Pio. 26

slon magrneto. Under this classification, therefore, any mag-
neto with which it is necessary to use a separate vibrator or
non-vibrator coil to produce a high-tension current is of the
low-tension type.

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'^w-
,^*,-^

30 ELECTRIC lONITION § 8

Inasmuch as the basic principle imderlying the operation
of low-tension magnetos is the same for all types, regardless
of variation in details of construction and application of prin-
ciple, no attempt will be made to describe in detail the special
characteristics of the many domestic and foreign magneto-
electric generators at present in use. A description of some
of the conmion types of machines will suffice to give a general
idea of the characteristics of all.

One type of low-tension alternating-current magneto is
shown in cross-section and longitudinal section in Fig. 26.
For a four-cylinder four-cycle engine, it is driven by gearing
at the speed of the engine, the gears being set so that the
range of the spark timer coincides with the effective range
of the magneto current. The armature positions deter-
mining the latter are marked on the magneto, and it is
unnecessary to change the angular relation of the armature
to the engine crank-shaft when the spark is advanced or
retarded. The principal features of construction are as
follows:

The permanent magnets a have pole pieces b fastened to
them by screws. The armature core c is wound with double
silk-covered magneto wire, and the ends of the core are
screwed to hard brass disks d, into which the two shaft
sections e are screwed and riveted. The object of this con-
struction is to make a neater and more compact winding of
the armature than would be possible if the shaft passed
through the core. One of the terminals of the armature
winding is insulated, and the other is grounded on the frame
of the generator. The insulated terminal of the coil is con-
nected to a hardened-steel bolt /, insulated by a mica bushing g
through the armature shaft, and the current is taken off by
a hardened-steel contact pin h in the brass mounting i, carried
by the hard-rubber tube ; screwed over the end of the bearing.
From i, a flexible connector leads to the binding post k. The
entire magneto is provided with an aluminum housing, com-
prising a sheet cover / and cast end plates m and n, together
with top and bottom plates o and p, and a cap q to exclude
dust. The shaft is lubricated by oilers r.

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§8

ELECTRIC IGNITION

43. A magneto of this type can be used either for low-
tension contact ignition or for supplying current to a coil of
the transformer, or non-vibrator, type for high-tension ignition.
For low-tension igni-
tion, no kick coil is
required, because the
magneto armature
has sufficient self-in-
duction to produce a
considerable spark
when the contact
points separate inside
the engine cylinder.
For high-tension ig-
nition, this magneto ^'o- 27

can be used with a suitable timer and either a transformer
type of coil without a vibrator for interrupting the primary
ctirrent, or with an induction coil having a magnetically
operated vibrator for interrupting the current. The arma-
tiu'e winding must be suited to the service required. The
binding post k is used for connecting the magneto to the
other apparatus of the ignition system.

44. Inductor Type of Magrneto. — An alternating-
current magneto of the inductor type, in which the armature
winding is stationary instead of rotative with the mechanically

driven rotor, or armature core, is
shown diagrammatically in side and
end elevations in Fig. 27. The rotor,
or armature core, as shown in Fig. 28,
consists of two arms ab and c d,
made up of thin sheet-iron punchings,
placed at right angles to each other;
they are connected by a short cylin-
drical neck whose axis is coincident

with that of the spindle on which the rotor turns when in place.
The position of the rotor in relation to the magnetic poles

is shown in Fig. 27. The coil k is placed around the cylin-

222—16

Fio. 28

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§8

drical portion of the rotor. The coil is wound spirally, like
a clock spring. The wire used is a flat ribbon of copper,
resembling a clock spring in cross-section, and is, of course,
insulated. This spiral armature coil is held stationary with
regard to the magnets. Its terminals are led out to stationary
binding posts or other smtable devices for making connection
with an external circuit.

45. The action of the magneto depends on varying the
number of lines of magnetic force through the armature coil.
The manner in which this is accomplished can be seen by

Pig. 29

referring to Fig. 29. In the position shown in Fig. 27, the
only magnetic flux that takes place is through the upper end
of the arm c of the rotor. There is no flux through the cylin-
drical portion that forms the core of the winding.

When the rotor has moved to the position shown in
Fig. 29 (a), the magnetic flux is from N to a, then through
the cylindrical neck to the arm c and out through c to 5.
The flux is from the front toward the back end of the rotor
when it is in the position (a). With the rotor in the position
(fe), all the magnetic flux that takes place is from N through
the upper end of a to S. On reaching position (^), the flux

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§ 8 ELECTRIC IGNITION 33

is from N through d to the cylindrical neck, then up toward
the front arm a and through a to S. In this case, the flux
through the cylindrical neck is from the rear bar c d toward
the front bar a fe, instead of from the front bar toward the
rear one, as in (a). On reaching its position (rf), the flux
through the cylindrical neck has again entirely ceased.

It will be seen that while the rotor has moved through one-
half revolution from the position shown by Fig. 27, to the
position shown at (d), in Fig. 29, the magnetic flux through the
center of the core of the winding k has been twice raised from
zero to the maximum value and dropped down to zero again.
Therefore, for a complete revolution of the rotor there are
four maximum values of magnetic flux. There are also four
times at which the electric current reaches its maximum in
the stationary winding during one revolution of the rotor.

46, What is known as the K-W magrneto is con-
structed on the principle just described. To facilitate
assembling and separating
the parts, one of the rotor
bars is made removable.
The machine is made to
run in either direction and
in any position, the oil cups
being arranged accord-
ingly. For jump-s park
ignition, it should be run
at a speed at least three ^^- ^

times that of the engine, so that under normal working
conditions it will have a speed of from 2,500 to 3,500
revolutions per minute. With these speed ratios, sufficient
current is generated on a quarter turn of the starting
crank to permit of starting the engine, thus obviating
the use of batteries for starting purposes. Because of the
impedance, or inductive resistance, of the coil and circuit, the
K-W magneto is self-regulating, so that, while at low speed,
it will generate enough current to start the engine with a
quarter turn of the starting crank; neither it nor the coil will

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§ 8 ELECTRIC IGNITION 35

be injured when the engine is speeded up, no matter how fast
it may be run. Four powerful sine waves of alternating
current are produced per revolution of the magneto, giving
sufficient power to operate the vibrator of the coil the instant
that the circuit is closed by the timer.

47. The stationary armature winding and the soft-iron
rotor of the Remy magrneto, which operates on the prin-
ciple just described, is shown in Fig. 30. In this design, the
rotor is placed between the magnetic poles in a manner
similar to that of the shuttle-wound armature already
described. There is, of course, only one complete electric
cycle per revolution, with its two maximum values of current.

Current is generated by means of a solid steel shaft a.
Fig. 31 (6), on which are mounted two steel inductor wifigs b
that revolve between the pole pieces of the three permanent
double U magnets c. Between the inductor wings is placed
a stationary winding or coil d of coarse magnet wire within
which the ciurent is generated. From this winding the cur-
rent flows to the transformer, or non-vibrator, coil on the
dashboard and thence back to the hard-rubber distributor e
on the face of the magneto. Just above the steel inductor
shaft a is the distributor shaft /, which is driven by the
inductor shaft through the pinion g and gear h. On the
extreme end of the distributor shaft / is a fan-shaped brass
segment t. Fig. 31 (a), that receives the high-tension current
from the coil through the high-tension cable connected
thereto. This segment revolves, passing the terminals of the
wires leading to the spark plugs.

The circuit-breaking mechanism is a double-lobed cam /
located on the end of the inductor shaft. The inductor shaft
travels at crank-shaft speed, and the double cam interrupts*
the circuit twice, therefore making two sparks for every
revolution of a four-cycle four-cylinder engine. The dis-
tributor shaft travels just half as fast as the inductor shaft;
therefore, there is one spark for every quarter turn of the
distributor shaft, or one spark as the brass segment passes
each terminal of the four wires found on a four-cylinder

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36 ELECTRIC IGNITION § 8

engine. In a six-cylinder engine, th^ magneto is geared to
run half again as fast as the crank-shaft. With relation to
the movement of the pistons the timing is thus fixed mechanic-
ally, a powerful, hot spark being produced in the cylinder
under compression at exactly the right instant, assuring
maximum engine power. The spark is advanced or retarded
by rocking the circuit-breaking cam housing k from right to
left, a timing range of 60° being provided.

As dry batteries may be wired through the transformer coil,
one type of dual ignition can be had with a single set of spark
plugs. When batteries are used, the engine may be started
on the spark without cranking, a push button being provided
on the coil, so that by merely pushing it inwards a hot spark
is delivered in the cylinder under compression.

I.OW-TENSION MAGNETO-IGNITION SYSTEMS

CLASSIFICATION AND ARRANGEMENT

48. There are several systems or methods of utilizing
the low-tension current primarily generated by a magneto.
The following are some of the principal ways of applying the
current generated in the low-tension winding of the magneto
armature, a condenser always being used to aid in producing
sudden variations of the primary current:

1. Interrupted primary current.

2. Short-circuited primary current.

3. Interrupted short circuit of primary current.

4. Condenser charge-and-discharge system.

49. Interrupted Primary Ma^rneto Current.— One

of the fundamental miethods of applying the current from a
magneto for jump-spark ignition is shown in Fig. 32. The
armature a of the magneto is wound with only one coil of
several turns. One end of the winding b is connected to the
frame of the machine, and the other end is led through the
hand switch c to the primary terminal d of the spark coil.

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ELECTRIC IGNITION

The primary-secondary terminal e of the spark coil is con-
nected to the insulated stationary contact piece / of the timer.
The arm g of the timer is connected to the frame of the
machine at the hinged end. The rotor h of the timer is shown
in the form of a two-lobed cam. The lobes of the cam lift
the arm g to break the primary circuit at the instant ignition
is required. One side of the condenser i is connected to the
wire joining e to the timer, and the other side is connected
to the frame, so that it is in parallel with the break in the
circmt made as the timer contacts 'separate.

The discharge of the condenser passes through the trans-

Pio. 32

former primary, the switch c, the magneto armature winding 6,
and thence to the frame and the other side of the condenser.
The spark plug ; is connected to the high-tension terminal k
of the transformer coil in the usual manner. If the timer
closes the circuit when the armature has made about a quarter
revolution from the position shown, the increase of current in
the transformer coil will be gradual compared with its
cessation, and no spark will be formed at the time of closing
the circuit.

60. If both the armature and the two-lobed timer rotate
at the same speed, the system will give a spark every half

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ELECTRIC IGNITION

§S

revolution; that is, of course, two sparks every revolution.
When the speed is the same as that of the crank-shaft of a
four-cylinder, four-cycle, single-acting engine, the spark will
be produced with the necessary frequency for the four spark
plugs.

A high-tension distributor is, of course, required when there
is only one transformer coil and more than one engine cylinder.

If the cam is filled in on one side, as indicated by the dotted
line, there will be only one spark produced every revolution.
If a cam filled in on one side, as just mentioned, rotates at
half the speed of the magneto armature, there will be a spark
produced every second revolution of the armature. With

Fio. 33

four timers of the latter nature, each breaking the circuit
every two revolutions of the armature, and four corresponding
individual transformers, the spark at the plugs can be pro-
duced with the required frequency for four spark plugs in a
four-cylinder four-cycle engine when the magneto armature
and engine crank-shaft rotate at the same speed.

The timer cam h can be fastened rigidly to the spindle of
the magneto without insulation, and the contact arm g of
the timer can be rotatively moimted on the part electrically
connected with the spindle. As shown, the arm g is electrically
connected to the frame of the machine, but the contact piece /

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ELECTRIC IGNITION

which can be carried on the same part as g, mounted con-
centric with the rotor A, must be insulated. The timer can
be rocked in the usual manner for varying the time o^ ignition.

51. Sliort-Circulted Primary Magneto Current.

With the arrangement shown in Fig. 33, all the armature
current passes through the primary winding of the transformer
when the arm g of the timer is not in contact with its insu-
lated contact piece /. The rotor h of the timer brings the
arm g into contact with / at the instant that a spark is to be
formed for ignition. The closed timer thus short-circuits
the transformer by furnishing another path of less resistance

Fio. 34

for the current of the magneto to travel through. The new
path is through the armature of the magneto to the contact
piece /, and then through g to the frame of the machine and
the opposite end of the armature winding. This latter circuit
offers far less resistance than the circuit through the trans-
former; nearly all the current therefore travels through the
timer on the short circuit when the timer is closed. The
sudden drop of current in the transformer primary at the
instant that the timer closes the circuit induces a spark at
the plug.

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§8

The condenser acts in practically the same manner as
indicated in the preceding examples, but it can be omitted
without, great injury to the contact points of the timer or
great modification of the strength of the spark.

The hand switch c is kept open during the operation of the
system. In order to stop sparking, the hand switch is closed.
The magneto armature is then practically short-circuited.
The armature of the magneto is wound and otherwise so
constructed that it will run on short circuit without injury
to itself or other parts of the apparatus.

Fio. 35

52, Interrupted Sliort Circuit of Primary Magneto
Current. — An ignition system depending for its operation
on an interrupted short circuit of the primary magneto current
is shown in Fig. 34. In this figure the same reference letters
that are used in Fig. 33 have been applied to similar parts.
The contact points of the timer are left together imtil the
primary current of the armature attains its maximum value.
On account of the low resistance of the short circuit through
the timer, nearly all the primary current passes through it.
Only a small amount of the current flows by way of the path

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S 8 ELECTRIC IGNITION 41

through the transformer, because the latter has a far higher
resistance in its primary winding than that of the short circuit
through the timer.

When the short circuit is broken by the mechanical action
of the timer, there is a sudden increase of current through the
primary winding of the transformer. This sudden increase
acts in the usual, manner to induce a high tension in the
secondary coil, so that a spark will jump at the plug. The
condenser must, of course, be correctly proportioned in order
to obtain good results.

53. Condenser Cliargre-and-Discliarg:e System*

Another system of applying low-tension magneto current for
jump-spark ignition is illustrated diagranmiatically in Fig. 35.
In this system, the electricity generated by the magneto
is first stored in a condenser i without passing any current
through the transformer; then, after the primary circuit of
the magneto is open, the condenser is discharged through the
primary coil of the transformer at the instant a spark is
desired.

The magneto winding is connected to the insulated contact
piece c of the primary circuit-breaker. The rotor d lifts the
circuit-breaker arm e at the time the magneto is giving its
full, or nearly full, current strength. The condenser i is thus
electrically charged. The timer arm / is not in contact with
the instdated contact piece g during the time of charging the
condenser. The rotor h lifts the timer arm / to make contact
with g and thus closes the condenser circuit through the
primary winding / of the transformer, whose high-tension
terminal is at k. At the instant contact is made at g, the
condenser discharges its current through the transformer,
and a spark is induced at the spark plug ;. By this arrange-
ment, the magneto circuit is connected to the condenser, and
the latter is charged by the magneto always at the same
time without regard to whether the spark at the plug is made
early or late by rocking the timer. The electric circuit from
the magneto is never closed so as to allow a circulating flow
of electricity.

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f«

As mentioned, the timer can be so mounted as to admit
of rocking it for varying the time of ignition. The circuit-
breaker can be mounted stationary, so as to be independent
of the rocking of the timer*

DUAIj IGKITION SYSTEMS

54* A low- tension magneto of the condenser charge-and-
discharge type for jump -spark ignition is illustrated in Fig. 36.
The armature has a laminated core o and rotates on ball
bearings. On the aniiature shaft is mounted the regular

Fic, 36

mechanically operated timer 6 of the interrupter type, which
has a twO'lobed cam for making and breaking the primary
circuit.

A second shaft c is run by the pinion and gear d and e at
one-half the speed of the annature, and carries a four-lobed
primary contact maker / and also the secondary current
distributor g. Fig. 37 shows the wiring connections. One
end of the armature winding is grounded on the core, as
usual, and the other is connected to the mechanically operated
interrupter b, and through the wire k to the primary of the
induction coil i. The other terminal of the primary is con-

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§8

ELECTRIC IGNITION

nected to the coil vibrator and also to the condenser ;. A
switch k has its blade connected with the other condenser
terminal, and has the three contacts connected, respectively,
to the vibrator / and the positive and negative terminals of
the battery w, as shown. The positive terminal of the battery
is grounded.

55. When the switch is in the position shown by the dotted
lines, and the circuit is closed by the primary interrupter 6,
a charge of electricity
passes through the wire h
and primary winding
of the coil i into the
condenser ;. As soon
as the condenser is
charged, which takes
but an instant, no fur-
ther current can flow,
because there is no
closed circuit connected
to the armature wind-
ing. The contact is then
broken, leaving the con-
denser charged, and at
the proper moment for
the spark a contact is
made by the timer /,
thus grounding the
wire h and permitting the
condenser to discharge
itself through the pri-
mary winding of the Pio- 37

coil i, the flow being now in the opposite direction to that of
the momentary charging current. The discharge of the con-
denser is so sudden as to induce a very high momentary
voltage in the secondary winding of the coil.

56. As one end of the secondary winding of the induction
coil is connected to the primary winding, the secondary wind-

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44 ELECTRIC IGNITION § 8

ing is grounded while the timer / is making contact. The
other end of the secondary winding is connected by the
cable n to the central terminal o of the high-tension dis-
tributor g, whose arm p, Fig. 36, is secured to the rotating
hard-rubber disk q attached to the shaft c. Four fixed ter-
minals, mounted in the same hard-rubber piece r that holds
the central terminal, distribute the current to the spark plugs.
As the end of the arm p is widened, no advance is required in
the distributor, and hence the timer /, Fig. 37, is the only
member moved to change the spark time, the condenser
simply remaining charged, between the moments of contact,
by b and /, respectively.

As already stated, the battery furnishes current for start-
ing, the switch k then being turned to the position shown
in full lines in the diagram. The magneto is thereby dis-
connected, and the battery current goes through the engine
frame, contact maker /, wire A, primary winding of the coil,
vibrator /, and the switch. The current can also go by way of
the armature winding and interrupter b ; but, if the vibrator is
adjusted for the current reaching the coil by the more direct
route, it will not respond to the weaker current. When the
engine reaches normal speed, the switch is thrown over by
the operator. The switch is of special design, and is very
highly insulated to protect the operator from shocks. It is
claimed that this magneto will produce a 3-inch spark in the
open air at 600 revolutions per minute, and a J-inch spark at
50 revolutions per minute. As only a single spark is pro-
duced, it can be timed with perfect accuracy.

As illustrated, the magneto is suitable for a four-cylinder
four-cycle engine when its armature rotates at the same speed
as the crank-shaft of the engine. For a six-cylinder four-
cycle engine, the armature must make three revolutions for
every two revolutions of the engine crank-shaft.

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§ 8 ELECTRIC IGNITION 45

HIGH-TENSION MAGNETOS

57, With reference to electric ignition, a lilgli- ten-
sion magneto, strictly speaking, is a magneto that delivers
electric current of sufficiently high voltage, or tension, to
jtunp the gap of a jump-spark plug under the usual con-
ditions of operation, the high-tension current being produced
and delivered without using any auxiliary coils or wiring
separate from the magneto. The high-tension magneto per-
forms all the functions of an electric generator, a timer, a
spark coil, and, for the usual case of four or more cylinders,
a distributor. It is really the embodiment of all these
individual parts in a single piece of apparatus.

MAGNETO WITH SINGLE ARMATURE WINDING

58. The Hess-Brl^ht M^li-tenslon mai^eto, shown
in sectional elevation in Fig. 38, operates on an interrupted
short-circuit system substantially the same as that described
in Art. 52 in connection with Fig. 34. The magneto has a
rotary armatiu'e with a single winding, generating a low-
tension current that passes through the primary winding of
a transformer that forms an integral part of the magneto.
The primary current generated in the armature a flows
through the insulated primary terminal b to the bridge c
by means of an interposed carbon button d that is held in
easy contact with the end of terminal 6 by a light stirrup
spring. One of the bolts e supporting the bridge c delivers
the current to branching circuits in the large, hard-rubber
block /. With the interrupter closed, current flows through
the fixed platinum-ended terminal g to the platinum-ended
interrupter lever A, to the magneto framing, and then to the
ground. With the interrupter open, the primary current is
conveyed to the transformer spool i through spool terminal ;.
This spool is encased in hard rubber and is further protected
by its location between the permanent magnets. The pri-
mary current leaves the transformer by way of terminal k

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§ 8 ELECTRIC IGNITION 47

which is in circuit with the ground through the frame of the
magneto. The terminal screws ; and k are secured by double
locknuts.

The secondary, or high-tension, current leaves the trans-
former by way of screw terminal /, and is carried by the
spring blade m to the distributor n, whose carbon brush o
delivers it in turn to the four terminal segments pi, p^, ps*
and p^ that are sunk into the large hard-rubber block /; these
segments are connnected electrically to the usual terminal
plugs q to which the spark-plug cables are connected. The
condenser r is located between the armature and the trans-
former spool. The lever 5 for timing the ignition projects
from the side of the magneto near the rear, or engine, end.
The distributor,' interrupter, and various other front parts
are enclosed by the large, solid hard-rubber cover t. Pushing
the detent spring levers u to one side permits the removal of
the cover and also tmcovers the oil holes.

The interrupter h is operated by the roll carrier v, which
raises the interrupter lever h twice in each armature revolu-
tion. The armature and timer are both mounted on ball
bearings.

For cutting off the ignition current, a terminal screw w,
electrically connected internally with the primary circuit, is
provided in the side of the large hard-rubber block of the
magneto. This terminal can be electrically connected to a
switch, preferably of the push-button type, conveniently
located. Closing the switch short-circuits the primary current
and thus stops the formation of sparks at the spark plug.

A jaw clutch X is provided for driving the armature. This
clutch has a number of teeth on its beveled inner end, so that
by loosening the nut y, the clutch can be rotatively adjusted
so as to bring the armature into the position of maximum
primary current at the proper instant relative to the time
a spark is to be produced.

The moving parts run in ball bearings that require little
lubrication, for which provision is made by holes protected
against the entrance of dust, thus insuring satisfactory
service with little attention.

222—17

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ELECTRIC IGNITION

§8

59. The general method of operation of the magneto in
its application to a four-cylinder engine, as shown by the
circuit diagram in Fig. 39, is as follows:

The primary current flowing from the winding on the
armature a is offered two paths; the shorter through the
interrupter h to ground and the longer through the primary
of the transformer spool i to ground. A third path through
the condenser r is apparently available, but the condenser
will not permit the passage of current. The condenser merely
absorbs a certain amount of current at the proper moment;

T tT T

r-.i_,J.„4

pj^^

Fig. 39

that is, at the instant of opening the interrupter. The inter-
rupter is closed the greater part of the time, allowing the
primary current to take the short path that the interrupter
offers. At the instant that the greatest current intensity
exists in the armature the interrupter is opened mechanically,
so that the primary current has no choice but to take the path
through the primary of the transformer spool. A certain
amount of current is at this instant also taken up by the
condenser r. This sudden rush of current into the primary
of the transformer spool induces a high-tension current in the

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§ 8 ELECTRIC IGNITION 49

secondary winding Si of the transformer. This high-tension
current is capable of bridging the space between the ter-
minals of the spark plug. The sharper the rush of current
into the primary winding of the transformer the more easily
will the necessary intensity of pressure for a jump spark be
induced in the secondary winding Sj.

60. The high-tension current induced in the secondary
winding is delivered to a distributor brush carrier n that
rotates in the magneto at the same speed as the cam-shaft
of the engine. This brush carrier slides over four metal
segments p^, p^, p^, and p^ set flush into the face of a large
hard-rubber block /. Each of these four segments connects
with one of the terminal sockets that are connected by cable
with the four spark plugs z. At the instant of interruption
of the primary current, the distributor brush is in contact
with one of the four metal segments and so completes the
circuit to that spark plug connected with the segment.

Should the circuit between the terminal ^i and its spark
plug be broken, or the resistance of the spark plug be too
great to permit a spark to jump, or should the discharge of
the high-tension current from the transformer be hindered
by any cause whatever, then the current might rise to an
intensity sufficient to destroy the transformer. To avoid this,
a safety spark gap z^ is introduced. This allows the pressure
to rise only to a certain maximum ; above this maximum dis-
charges take place across the safety gap. In this type of
magneto the spark discharges across the safety gap are visible
through a small glass window conveniently located in the top
of the hard-rubber block.

MAGNETO WITH DOUBLE ARMATURE WINDING

61. What is popularly known as the U. & H. high-ten-
sion magrneto, shown in sectional elevation in Fig. 40, has
a rotary, double-wound armature of the shuttle type. The
primary current is interrupted to induce a secondary high-
tension current. The primary winding of the armature.

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Fig. 40

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§ 8 ELECTRIC IGNITION 51

which is the inner coil, consists of a few layers of coarse
insulated wire, and the secondary winding consists of a great
number of layers of very fine insulated wire. The primary
current passes through only the timer and primary winding
of the armature. The condenser is in parallel with the timer
or interrupter. The secondary circuit comprises a slip ring
connected to the secondary winding of the armature, a col-
lector brush, a high-tension distributor, a spark plug, and
both the secondary and primary windings of the armature.
A safety spark gap is used on the high-tension circuit.

62. One end of the primary winding is grounded to the
armature itself, while the other end is connected with the
carbon brush a, which is carefully insulated from the arma-
ture shaft. Brush a bears against the interrupter block
screw 6, which in turn conducts the current to the interrupter
block c and to the condenser plate d. From the interrupter
block c the current is conducted to the interrupter lever.
This lever is in metallic contact with the body of the magneto,
and is therefore grounded, so that when the interrupter lever
is in contact with the interrupter contact screw, the primary
circtiit is completed, and the primary winding of the armature
is short-circuited.

63. The beginning of the secondary winding is connected
to the end of the primary winding, being, in fact, a con-
tinuation of the primary winding. The end of the secondary
winding is connected to the armature slip ring e, which is
thoroughly insulated from the armature. From the arma-
ture slip ring the high-tension current is conducted, by means
of the brushes / to the distributor slip ring g whence it is
led to the distributor brush h by means of the distributor
stem i and the distributor brush spring seat ;. The distrib-
utor plate k is provided with as many brass distributor
segments, evenly spaced around the distributor bore, as there
are cylinders to be fired, and as the distributor brush is
revolved, it comes into successive contact with the distributor
segments. The distributor segments are in turn connected
with the secondary terminals located at the top of the dis-

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52 ELECTRIC IGNITION § 8

tributor plate, and of which there are also as many as there
are cylinders to be fired. From the secondary terminals the
high-tension current is conducted by cables to the spark plugs
of the proper cylinders. The current, in leaping the gap of
the spark plug, is conducted to the grotmded end of the plug,
from which place it returns to the grounded end of the primary
winding, through the primary winding to the beginning of the
secondary winding, thereby completing the secondary, or
high-tension, circuit.

64, At the instant of the interruption of the primary
circuit, a secondary, or high-tension, ciirrent is induced in the
secondary winding. The intensity of the current induced in
the secondary winding is nearly proportional to the intensity
of the current generated in the primary winding; hence, the
maximum secondary effects are produced when the primary
current is interrupted at its maximum, or just as the armature
passes from one pole to the other.

Owing to its rotation in the magnetic field, the high-tension
winding generates a current in a manner similar to that
of the low-tension winding, but this current is of far greater
intensity than the primary current, owing to the difference
in the windings. The tension of this current is not sufficient,
however, to cause it to leap the gap of the spark plug, but at
the instant of interruption of the primary current, the induc-
tive effects are such as to raise the voltage or pressure of this
current to a point that will enable it to leap the gap of the
plugs. The electrical effects induced by the interruption of
the primary current are of much shorter duration than those
generated by the rotation of the secondary winding; therefore,
the generated current has its voltage increased for but an
almost infinitesimally short time. This temporary increase
enables it to bridge the air gap of the plugs, and, once bridged,
their resistance is reduced to such an extent that the current
generated by rotation, and which lasts an appreciable time,
can continue to cross. This results in a continuous flame
across the spark plug gaps and on account of its high temper-
ature and large voliune, the flame has strong ignition qualities.

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§8

ELECTRIC IGNITION

65. The interrupter, as shown in Fig. 41, consists of the
interrupter plate a located in the interrupter housing h.
Attached to the interrupter plate is a stud c on which is
pivoted the interrupter lever d. The interrupter lever is
provided with a platinum-pointed contact screw e, and is nor-
mally held by the flat spring / in contact with the platinum-
pointed interrupter contact screw g. The interrupter contact
screw is connected to the end of the primary winding.

Keyed to the interrupter end of the armature shaft, and
rotating positively with the armature, is the interrupter-cam
housing /, Fig. 40. Securely attached to the interrupter-cam

Fig. 41

housing is the interrupter cam, consisting of a ring of hard
fiber, having on its inner face two projections, or cam faces.
The interrupter housing 6, Fig. 41, is held in accurate
alinement with the interrupter cam by the construction of
the rear. end plate, and as the armature revolves the pro-
jections of the interrupter cam are brought into contact with
the interrupter cam pin A, causing a movement of the inter-
rupter lever d sufficient to separate the contact screws e and g
and thereby interrupt the primary circuit twice in every
revolution. As the projections continue to revolve, the
interrupter lever d instantly resumes its normal position, and
completes the primary circuit.

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54 ELECTRIC IGNITION § 8

66. The safety spark gap m, Fig. 40, is formed by bring-
ing the distributor-cover screw n to within a certain distance,
which is generally about | inch, from the end of the distributor
stem o. The distributor cover screw is grotmded to the mag-
neto, thereby providing a path for the high-tension current
should the voltage become high enough to cause it to leap the
safety spark gap. The user is cautioned against allowing
the discharges to pass across the safety spark gap for any
length of time, as it places the high-tension insulation imder
a continuous and abnormal stress.

67. A starting device is proviided with this magneto.
It is arranged for furnishing a current and spark strong
enough to produce ignition in the cylinders even when the
shaft that is driving the magneto is rotating at very low speed ;
that is, even though the rotary movement of the driving shaft
is so slow as to be practically imperceptible. This is accom-
plished by the use of an automatic lock for the armature and
a coiled spring />, Fig. 40, between and attached to the arma-
ture driver q and the driving flange r for driving the armature.
When the armature driver is rotated slowly, the armature is
locked, so as to prevent its rotation during part of a revolution
of the shaft. The coiled spring is still further coiled against
its resistance during the time the armature is locked and its
driving shaft is rotating slowly. The armature is then auto-
matically released and snapped forwards suddenly by the
uncoiling of the spring. The movement of the armature
secured in this manner is rapid enough to produce a spark
in the cylinder under compression. The construction is such
that the release and spark occur at the proper time for ignition
when starting the engine by hand cranking. As soon as the
speed is increased by an impulse in the engine cylinder, the
device that temporarily locks the armature is thrown out of
action and the armature rotates with its driving shaft.

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§8

ELECTRIC IGNITION

\J^^

=s.U

1 J

V'^ '^^=^y 1

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-^-

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Aj^

MAGNETO WITH STATIONARY ARMATURE

68. The Boscli lil^li-tension mafirneto has a sta-
tionary double-wound armature and a rotary magnetic screen
of the form shown in Fig. 42. It is operated on the inter-
rupted primary-current system. The armature a is stationary
in the position shown, and it is enough smaller than the pole
pieces h to permit a soft-iron segmental screen c to pass
between them. The segmental screen pieces are mechanically
motmted on non-magnetic heads, to which the spindle or the
shaft is attached. The effect of this screen is to divert the
lines of force at each eighth of a revolution, sending them
alternately through
the stem of the
armature core and
through the ends,
as shown by the
dotted arrows. This
reverses the current
four times in each
revolution instead of
twice, as is the case
with the ordinary
rotating shuttle-
wound armature.

69. Referring to Piq- «

Fig. 43, which is a sectional elevation of the magneto,
and to Fig. 44, which is a conventional wiring or circuit
diagram, it will be seen that one end of the primary
winding is electrically connected to the armature core a and
that the other end is connected to the brass tube 6, which
is mounted in the rear portion of the armature spindle and is
insulated through it. The conductirig bar c is firmly secured
to this tube, the end of which extends beyond the spindle of
the armature, and the primary current is conducted by means
of the bar c to the contact piece d, which is provided with a
platinum contact screw e. A contact piece in the upper end

ft 1

TT^

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/ ^

J^Wmm^

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)

1 *

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ELECTRIC IGNITION

§8

of the interrupter lever / is normally held against the screw e
by action of the compressed spring g. A recessed disk h
rotates with the magnetic shield i. The lobes on the disk h
strike the lower end of the interrupter lever / and move it so
as to break the contact between the lever and screw e. The
interrupter lever is in electrical contact with the frame of the
machine, and consequently with one end of the grounded
primary winding. When the interrupter lever / is in contact
with the screw e^ the circuit is closed through the brass tube 6,

Fig. 43

the conducting bar c, the contact screw e, the lever /, the
frame of the machine, and the core of the armature. One
of the terminals of the condenser / is connected to the con-
tact piece d, and the other terminal is connected to the body
of the machine. The condenser is thus connected in parallel
with the contact breaker.

70. The secondary winding is a continuation of the
primary winding, their adjacent ends being soldered together.
The other end of the secondary winding is connected to the

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§8

ELECTRIC IGNITION

small insulated tube k. The bent carbon holder / passes
through the rear portion of the armature spindle; one end
of the carbon holder is fitted into the insulated brass tube k
by means of a small plug. The secondary current passes
from the armature through the small plug and bent carbon
holder to the carbon brush m, which conducts the current to
the slip ring n of the high-tension distributor disk o. The
distributor segment p may be considered as a distributor
arm that comes successively into contact with the four
high-tension carbon distributor terminals q. Each of the

Fig. 44

terminals q is connected to its own insulated tubular con-
ductor in the terminal block. Above the terminal plate is
a removable plug contact piece that carries four insulated
plugs, each of which slips into contact with its tubular mate
in the terminal block. The upper ends of the plug contact
pieces are threaded so as to provide for making screw con-
nections to the wires leading to the spark plugs.

71, The path of the high-tension current is through the
secondary winding of the armature, the brass tube A, the
bent carbon holder /, the distributor disk o, the current-
collecting carbons in the carbon holder g, the conductors in

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58 ELECTRIC IGNITION § 8

the terminal block, the plug contacts, the wire leading to the
ignition plug, the engine, and the frame of the machine to
the armature core, and then through the primary winding
to its junction with the secondary winding.

A safety spark gap 5 is provided between the low-tension
conducting bar c and the high-tension carbon holder /. This
allows a spark to jump between the extended ends of the
primary winding when an excessive pressure occurs.

The speed of the rotor of the magneto, when supplying cur-
rent to the four spark plugs of a four-cylinder four-cycle
engine, is the same as that of the half-speed shaft, or cam-
shaft, of the engine. This speed is only half as fast as the
speed of the crank-shaft. For a two-cylinder four-cycle
engine, the magneto rotor can be run at the same speed as for
a four-cylinder engine of the same type, two of the high-
tension terminals being short-circuited to the frame or body
of the magneto. In a two-cycle four-cylinder engine, the
magneto speed is the same as that of the crank-shaft.

72, The mechanical connection for rocking the timer by
hand is made at the arm r. Fig. 43. The four- terminal timer
shown is constructed to rock 30°, corresponding to 60° rotation
of the crank-shaft in a four-cylinder four-cycle engine. The
same angle values apply to a two-cylinder four-cycle engine
using only two of the high-tension terminals. On a four-
cylinder two-cycle engine, the angles of the timer rock and
crank-shaft rotation are equal. When the magneto is pro-
vided with six high-tension terminals for a six-cylinder engine,
instead of four terminals as illustrated, the magneto rotor
speed is one and one-half times that of the cam-shaft for a
four-cycle engfaie ; the magneto rotor makes three revolutions
during four revolutions of the engine crank-shaft. In the six-
cylinder four-cycle engine, a 30° rock of the timer corresponds
to 40° rotation of the crank-shaft.

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60 ELECTRIC IGNITION § 8

MAGNETO WITH STATIONARY WINDING

73. The Plttsfleld hi^h-tension magneto, which
has a stationary winding, is illustrated in Fig. 45 (a) and (6).
The north and south pole pieces of the permanent magnet are
at N and 5. A magnet core made up of soft-iron stampings
and placed at right angles to the permanent magnet has its
laminated pole pieces E and F located as illustrated. A
non-vibrating induction coil c is located on what corresponds
to the crown of the magnet core. A rotor somewhat in the
form of the magnetic screens referred to in Art. 68, but
thicker radially, lies in the bore between the magnet poles.

The laminated soft-iron rotor a b revolves in the magnetic
field produced by the permanent magnets. The rotation of
the armature a 6 in the magnetic field generates in the wind-
ing of coil c an alternating current that attains a maximum
value four times during a complete revolution of the armature.

74. The primary winding, which is next to the core d,
consists of a few turns of heavy wire; one end of this wire is
connected to the body of the machine, and the other end is
connected to a contact plate insulated with hard rubber.
From this plate a wire makes a connection to the contact
piece and platinum screw of the interrupter, the contact piece
being insulated from the interrupter, which is in metallic con-
nection with the field or ground. The current generated in
the primary winding is therefore short-circuited as long as the
contact piece and platinum screw of the interrupter are in con-
tact with each other. The primary current is interrupted
at the instant that the interrupter cam e moves the interrupter
lever. A condenser /, protected by an aluminum housing g,
is connected in parallel with the contact points of the
interrupter.

75. The beginning of the secondary winding, which con-
sists of many turns of fine wire, is connected to the end of the
primary; the other end leads to contact button h of the coil.
The secondary current is conducted from button h to the brass
distributing segment i by means of the carbon brush and its

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J 8 ELECTRIC IGNITION 61

spring ;', to the conductor k, which is insulated by hard-rubber
piece /, and to the distributor segment i. The segment i is
insulated by the hard-rubber piece m. In the front end plate n
are inserted four high-tension terminals. During a revolution
of the rotor the segment i comes into successive contact with
all the high-tension terminals. From the high-tension ter-
minals the ciurent is conducted to the socket inserts in the
distributor plate o by means of connections p. From the
socket inserts the high-tension current is conducted, by means
of cables, to the spark plugs of the cylinders in the order
required. The interrupter is screwed on one of the heads of
the magnetic screen, and can be easily removed. The primary
circuit is four times interrupted and short-circuited during
each turn of the armature. This is accomplished by means of
the four-lobed cam e rocking the interrupter lever. This cam
revolves with the rotor of the magneto.

76. The four sections q of the magnetic screen are
mounted on non-magnetic heads concentric with the rotor.
The interrupter lever, together with the contiguous parts of
the interrupter, is mounted on one of these heads. The time
of ignition is varied by rocking the interrupter and the mag-
netic screen on which the interrupter is fastened. For this
purpose the screen sleeve q is fitted with a lever to which con-
nections leading to the spark control can be attached. The
time adjustment is 30° at the timer, which corresponds to 6CP
at the engine crank-shaft of a four-cylinder four-cycle engine.

77, The action of the magneto depends on the alternate
magnetizing and demagnetizing of the magnet core on which
the coil c is mounted, thus inducing an electric current in the
coil. This is accomplished by bridging the air gaps between
the permanent magnet poles and the poles of the soft-iron
laminated magnet core on which the transformer coil is
mounted. The manner in which this occurs during the
rotation of the rotor, can be seen by referring to Fig. 46.

In Fig. 46 (a) the position of the rotor is such that the few
magnetic lines that pass through it go from N to S without
passing into the soft-iron magnet. When the rotor has turned

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ELECTRIC IGNITION

§8

to the position shown in (6), the magnetism flows from the
permanent pole N through the side b of the rotor to the pole F
of the soft magnet core. From F the magnetism flows
through the core of the transformer coil c, Fig. 45 (fe), and on
to the pole E. From E the path of the magnetic flux is
through the side a of the rotor to the pole S of the permanent
magnet. When the rotor reaches the position shown in (c) there
is practically no magnetic flux through the induced magnet.

Fio. 46

Any flux that occurs follows the path indicated by the arrows.
In the position of the rotor shown in (d), the magnetic flux,
as indicated by the arrows, is through the soft magnet core
and the transformer in a direction opposite that shown when
the rotor is in the position (6). A complete cycle, compri-
sing two reversals of the current and the corresponding two
maxima of positive and negative pressures, takes place dur-
ing a half revolution of the engine. The current therefore
has maximum values four times per revolution of the engine.

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TRANSMISSION AND CONTROL
MECHANISM

TRANSMISSION MECHANISM

CliUTCHES

PURPOSE OP CLUTCHES

!• In an automobile driven by an internal-combustion
engine, means must, be provided for connecting the engine
to the transmission gearing or disconnecting it from this
gearing, either while the gears are being shifted or when the
car is to be started or stopped. This is necessary because
an internal-combustion engine cannot be started under a
full load. For the purpose named, a friction clutch of some
suitable form is employed in nearly all cars. The clutch
forms a separate member in most cars, but in others it is
incorporated with the gears by which the speed of travel of
the car is regulated.

2. Some of the most important qualifications that the
friction clutch must fulfil in order to give satisfactory operation
in automobile service are as follows:

1. It should engage without seizing and jerking the car,
whether the closing force is allowed to act slowly or almost
instantly.

2. It should hold without slipping after the car has been
started and the clutch is in full engagement, except under

COrritlOHTCO by INTCRNATIONAL textbook company. BNTBRCD at •TATIONCRa* HALL. LONDON

§9
222—18

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2 TRANSMISSION AND § 9

very unusual conditions in which the speed of rotation of the
road wheels is very suddenly checked or increased.

3. It should release instantly, without dragging the
driven parts around, as soon as the disengaging mechanism
is operated.

4. It should be of such form that the driven side will
have a minimum tendency to keep rotating by its own momen-
tum after the clutch is released. In other words, the flywheel
action of the portion of the clutch that is connected to the
power-transmitting mechanism should be a minimtun.

5. It should not require constant adjustment and atten-
tion, with regard to the presence or absence of a lubricant,
to keep it operating projperly.

6. There should also be fulfilled the usual conditions
desirable in any class of machinery; that is, all parts should
be of proper strength and possess lasting qualities.

Although there are many clutches that fulfil the preceding
conditions as to satisfactory operation when properly adjusted
and lubricated or free from lubricant, there still appears to
be none that will operate satisfactorily if the lubricant is not
of proper quahty or the clutch runs dry, provided it is of the
type requiring a lubricant; also, clutches intended to operate
without any lubricant on the friction surfaces are liable to
give trouble if some lubricant accidentally reaches these
surfaces or if the friction materials become hardened or
charred by use.

3. The friction clutches used in automobiles may be
broadly divided into three general classes, namely, cone
clutches, disk clutches, and band clutches.

CONE CLUTCHES

4. The elements of a cone clutcli are illustrated in Fig. 1.
At a is shown the driving shaft, which may be taken as the
end of the crank-shaft of the engine; at 6, the driven shaft
through which power is transmitted to the driven road wheels ;
and at c, the external cone of the clutch, and at d, the internal

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§9

CONTROL MECHANISM

cone. The external cone c is rigidly keyed to the driving
shaft. The internal cone d is free to slide on the shaft 6, but
is prevented from rotating on it by the key e. If the external
cone is rotating and the internal cone d is pressed in toward
it, the conical surfaces at / and g will be brought together.
The friction of these surfaces against each other will cause the
external cone c to transmit a turning effort, or torque, to the
internal cone d, and thus cany this cone around with it.
The extent of this tendency to drive the internal cone is
proportional, at least in a measure, to the pressure between
the conical friction surfaces at / and g. On account of the
conical shape of the friction surfaces, there is a wedge-like
action that gives a pressure be-
tween them that is much greater
than the force that pressed the
driven cone toward and against
the driver. For a given force
acting to press the inner cone
toward the outer one, the more
nearly the conical surfaces
approach a cylindrical form,
the greater will be the pressure
between them.

5, By the use of this de-
vice, the car can be started
gently by forcing the inner Fio. i

cone gently in toward the outer one and allowing the latter
to slip around over the driven cone, but at the same time
gradually starting it to rotate and increasing its speed of
rotation. The rotation of the* driven cone is, of course,
resisted by the force required to start and move the car.
After the rate of travel of the car has become such that
both cones rotate at the same speed, they can be forced
together harder in order to prevent slipping.
• When the inner cone d. Fig. 1, is transmitting turning effort
to the driven shaft fe, the hub of the cone, of course, presses
against the side of the key e. On account of the friction due

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TRANSMISSION AND

§9

to this pressure between the hub and the key, the cone is
prevented from sliding freely along the shaft b. The pressure
and resistance to this sliding is greater as the turning effort
transmitted becomes greater. The friction between the cone
hub and the key e makes it difficult — sometimes impossible
— to increase the pressure between the friction surfaces
gradually, because the tendency of the cone is to slide on the
shaft with an intermittent, or jerky, motion and thus suddenly
increase the pressure between the friction surfaces as the cones

are brought into engage-
ment. This in turn causes
sudden gripping and start-
ing of the driven cone and
consequent jerking of the
car and straining of the
machinery. For this
reason, cone clutches on
automobiles generally do
not have the sliding cone
move over a shaft with a
key, which is naturally at
a small radial distance
from the center of the
shaft, but are so con-
structed as to have the
parts through which the
P»G 2 turning effort is transmit-

ted from the cone to the shaft located at some distance from
the shaft. The friction surfaces are generally made of
materials that have a greater frictional resistance to slipping
than have two pieces of metal when pressed together.

6. Fig. 2 shows an internal cone covered with a leather
band that is held in place with rivets. The frictional clinging
of leather to a metal surface against which it rubs is greater
when the leather is in proper condition. The outer surfacd
of the leather shown in the figure presses against the inner
surface of the external cone when the clutch is engaged.

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CONTROL MECHANISM

On account of the greater friction^l resistance to sliding
between leather and metal, they are said to have a higher
coefficient of friction than has metal on metal.

such as is used
Fig. 3. At a is

7. A leather-faced cone clutcli,

on automobiles, is shown in section in
shown the end of the ^
engine shaft- and at b
the coupling by means
of which power is trans-
mitted to the parts that
connect to the road
wheels. The external
cone c is part of the fly-
wheel in this case. The
flywheel is bolted to
the flange at the end of
the engine shaft. To the
internal cone d is fas-
tened a leather facing /.
At g is shown a part
that in effect forms an
extension of the engine
shaft. On the end of
this extension is a nut h
against which bears one
of the races i of a ball
thrust bearing. One ball p
of this bearing is shown |
at /. A coiled compres- |
sion spring k bears
against the other race of
the ball thrust bearing, and also against the hub of the cone d.
The expansive force of this spring tends to move the cones
toward each other and thus press the friction surfaces together.
The clutch is thus held in engagement while the power is
being transmitted through it. For the released position of
the clutch, another ball bearing, in which the ring / forms one

Fig. 3

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6 TRANSMISSION AND § 9

of the races, is provided. The ring / is connected to a yoke m
by means of the pins n. When the yoke is drawn away from
the flywheel, it pulls the internal cone d with it against the
resistance of the coiled -closing spring, and thus separates the
friction surfaces so that the clutch is released. The shaft g
and the nut h then rotate inside the hub of the internal cone,
and the balls / of the thrust bearing roll around on their races
under a load equal to the expansive force of the closing
spring k. At o is shown a grease cup used to lubricate the
bearing between the shaft g and the hub of the internal cone.
As will be seen, the clutch normally stands in the closed, or
engaged, position, and force must be exerted to release it.

Fig.

8. One form of clutch-releasing mecliaiilsin is

shown in Fig. 4, in which the releasing pedal is shown at a;
the arms of the internal cone, at b; the ring, or collar, of the
releasing collar bearing, at c ; and links connecting the collar c
to crank-arms of the pedal shaft e at d. This shaft is sup-
ported by the frame of the machine, which is not shown.
Pressure of the foot on the pedal draws back the internal cone
and releases the clutch.

9. A reversed cone clutcli is illustrated in Fig. 5, in
which the engine shaft is shown at a and the driven shaft

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CONTROL MECHANISM

at b. The flywheel has fastened to it the external member c
of the clutch with which the leather-faced internal cone d
engages frictionally. The turning effort received by the
cone d is transmitted to arms e, through each of which a pin
passes in order to connect it to the internal cone. The clutch
is held in engagement by the expansion spring /, which tends
to force the internal cone away from the hub that carries the
arms e; the cone friction surfaces are thus held in engagement.

The turning effort is transmitted through the arms e to the
hub to which they are attached and then through the sleeve
extension of this hub to the coupling g, which is fastened to
the shaft b. It may be noted that in this clutch the slipping
movement necessary to release the clutch takes place at the
pins passing through the outer ends of the arms e. These
pins are at a considerable distance from the clutch shaft, and
therefore have a minimum pressure against them for trans-
mitting the power from the internal cone to the other parts

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TRANSMISSION AND

§9

of the driving mechanism of the car. This design is a very
effective one for eliminating the objectionable feature regard-
ing the pressure of the cone hub against the key of the shaft
on which it slides, as pointed out in connection with Fig. 1.

10. In order to secure means of bringing a cone clutch
into engagement gently, various methods of causing a portion
of the leather friction surface to come first into contact with
the outer cone, and then later all the leather facing into
engagement, have been put into use. One of these devices,
which is characteristic of this method of eliminating more
or less the tendency of the clutch to seize and jerk, is shown

in Fig. 6. In this figure, a part of the metal of the internal
cone is shown at a and the leather facing at b. A plunger c
is set into the metal of the cone and is forced out by an
expansion spring d against the inner side of the leather.
This presses out the portion of the leather that is over the
end of the plunger, so that it stands higher than the other
parts of the leather facing. Several of these plimgers are
used in the complete cone. When a clutch thus constructed
is brought into engagement, the high portions of the leather
facing first come into contact with the external cone ; thus, the
pressure against the leather is limited to the expansive force

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§y

CONTROL MECHANISM

of the springs on the plungers. The clutch therefore does not
grip suddenly and jerk,- even though the sliding motion of
the internal cone is intermittent and irregular.

The same effect is secured in a somewhat similar manner by
cutting holes through the leather facing and inserting pieces
of cork whose outer ends project slightly" above the face of
the leather. The cork, if of good quality, is easily com-
pressed, so that it has about the same action as the leather
forced out by the plunger. The tendency to cling is some-
what higher for the cork than for leather in the condition that
ordinarily exists in service. Clutches fitted as just described
are known as cork-insert clutches.

II. The angle between the cone surfaces and the shaft,
or axis, of the cones, is generally made as small as is possible
without getting the cone surfaces so nearly cylindrical as to
cause them to stick together
unduly and thus prevent ready
release of the clutch. The angle
is generally not less than 6° nor i

greater than 12°.

DISK CLUTCHES

12, In Fig. 7 is shown a
simple form of disk clutch.

It consists of an engine shaft a

and a driven shaft 6, to which

power is transmitted by the

friction disks c and d when their

flat adjacent surfaces are fig 7

pressed together. If the friction surfaces are made entirely

flat so as to cover the complete areas within the circles

that form the outlines of the disks, the tendency is for

the wear, due to slipping, to be more rapid toward the

periphery than at and near the center of the disk. In order

to obviate this undesirable feature, which reduces the

amount of turning effort that can be transmitted from one

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TRANSMISSION AND

§9

disk to the other, the disks are hollowed out so that the
friction surfaces form two rings at the periphery of the disk.
Although, when modified in this manner, the bearing surfaces
are no longer in the form of disks, the name disk clutch is
universally applied to clutches of this type. Since the bear-
ing surfaces are flat and are at right angles to the direction of
the force that is applied to close them, the pressure between
the friction surfaces, instead of being greater than the closing
force, as in cone clutches, is equal only to the amount of the
closing force. Therefore, for a given mean diameter, an equal
extent of friction surfaces, and the same closing force, a single

Fig. 8

pair of frictional surfaces will not transmit as much turning
effort in the disk type of clutch as in the cone type. In order
to keep down the size of the disk clutch, as well as the closing
force, a number of friction disks, or rings, are customarily used.

13. Fig. 8 shows a multiple-ring, or multiple-disk,

friction clutcli, the driving member being shown at a
and the driven shaft at b. The driving member a has two
arms c that engage with a number of the larger disks d in such
a manner that the disks are free to slide on the arms c, but
must rotate with them. Between each adjacent pair of these
larger disks lies a smaller disk e, which is in similar engage-

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§9

CONTROL MECHANISM

ment with the inner member of the clutch. The inner
member is connected to the driven shaft b and rotates with it.

Flo. 9

Fio. 10

One of the outer, or larger, disks is shown in perspective in
Fig. 9. The two notches that engage with the arms that

Fig. 11 Fio. 12

drive it are shown at n. The side view of the disk is shown
in Fig. 10, where it is in engagement with the driving arms c.

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12 TRANSMISSION AND § 9

One of the smaller, or inner, disks is shown in perspective in
Fig. 11. It is smooth and circular outside, but the central
hole is notched, as shown at a, to fit the inner, or driven,
member of the clutch. This member is shown in place at /,
in Fig. 12. The circular hole through the larger disk is large
enough to clear the fathers g on the driven member /.

Referring again to Fig. 8, at h is shown a closing plate that
is pressed against the end disk by the closing spring t, which
acts expansively. All the friction surfaces are therefore
pressed against one another with a pressure equal to the
expansive force of the closing spring i.

The multiplication of the friction surfaces in this manner
increases the turning effort that the clutch will transmit in
the same proportion as the number of pairs of frictional
surfaces is increased. Thus, with two pairs of frictional

. . surfaces, the turning

/ ^ \ b effort will be twice

as great as with one
pair, as shown in
Fig. 7, provided, of

P'°- 13 course, the friction

surfaces are of the same mean diameter and extent, have
the same coefficient of friction, and are pressed together with
the same pressure in each case. Thus, if there are thirty pairs
of friction surfaces, the clutch will transmit thirty times the
turning effort that it would transmit with only one pair.

14. An idea of the extent of increase of frictional effect
that is secured by increasing the number of pairs of friction
surfaces can be obtained by the following simple experiment:
As shown diagrammatically in Fig. 13, lay together a number
of sheets, or slips, of writing paper on a board or a box so that
the ends of alternate sheets will overlap each other half way
or more, and place a weight, as a, of half a pound or more on
top of the overlapping parts. The sheets are shown separated
merely to make the illustration clear; they really touch each
other. Grasp the free projecting ends b and c of the paper
and pull the sheets apart in opposite directions, as indicated

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§9

CONTROL MECHANISM*

by the arrowheads, so that the overlapping sheets slip from
between each other. Care should be taken not to lift or pull
upwards so as to raise the paper and weight. First use two
or three sheets; then increase the number of sheets to thirty
or more. The amoimt of pull necessary to draw apart thirty
sheets will be rather surprising at first. This pull, as was
stated in Art. 13, is proportional to the number of pairs of
surfaces that slide, or rub, over each other when the sheets are
pulled apart.

15, After the disks of a multiple-disk clutch have been
pressed together, there is a tendency for them to stick, or

Fig. 14

cling, to each other so as not to separate freely. This sticking
together is very marked when oil is used, as is customary
when the disks are of metal. Therefore, some means is
generally provided to force them apart when the clutch is
released by drawing back the closing plate h, Fig. 8. The
disk shown in Fig. 9 has four strips partly cut from the rest
of the metal and bent up as shown. When the disks are
assembled in the clutch, these bent-up ends press against the
next large plate, as shown in Fig. 14, where the clutch is in
the open, or released, position. By this means, the large

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TRANSMISSION AND

§9

plates are held apart and at least one pair of the friction
surfaces lying between the two large plates is separated.
When the clutch is closed, the ends of the bent-up strips
spring down. In addition to overcoming the sticking tend-
ency of the friction surfaces, these bent strips must overcome
the frictional resistance to the sliding of the large disks along
the arms c. Fig. 14, that drive them, as well as that to the

sliding of the small
disks along the feathers
g, g, Figs. 10 and 12, that
drive the small disks.
If the clutch is trans-
mitting considerable
power at the instant it
is released, there is con-
siderable • Irictional re-
sistance to the sliding of
the disks along these
parts; therefore, the
separating springs, that
is, the bent-up strips,
must have considerable
strength in order to
force the disks apart
promptly. Owing to
the causes just men-
tioned, a clutch of this
type always has some
Pig. 15 tendency to drag after

the releasing plate has been drawn back.

aaaia.:r

16. In some designs of multiple-disk clutches, one set of
the disks is made of metal faced with leather and the other
set is made entirely of metal. It is not customary to use oil
in a clutch having leather-faced disks, in which case the
sticking tendency due to the presence of oil is eliminated.
In one design of multiple-disk clutch, one set of the disks has
cork inserts. These inserts, on account of the elasticity of the

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§9

CONTROL MECHANISM

cork, tend to separate the disks when the closing force is
removed. When one set of disks is leather-faced or provided
with cork inserts, the number of sets required is not so great
as when metal-to-metal friction surfaces are used.

17, Fig. 15 shows a multiple-disk clutch with the closing
spring placed inside the friction disks. The casing a is
attached to the flywheel of the engine, and the shaft b trans-
mits the power to the driving mechanism of the automobile.
In this clutch, the cylindrical part c of the casing has a number

Fig. 16

of feathers or grooves that engage with corresponding parts
of the large disks to drive them. The small disks engage
with a drum d that is either feathered or grooved to engage
the disks. The expansive force of the closing spring presses
the drum d toward the right and the casing c toward the left.
The end plate e rests against a flange on the drum d] therefore,
as the latter is forced toward the right, the plate e is pressed
against the end friction disk. At the same time, the cover /
of the casing is pressed against the friction disk at the opposite

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TRANSMISSION AND

§9

end of the series of disks. The clutch is released by pressing
the drum d in toward the fljnvheel end a of the casing.

Some multiple-disk friction clutches are made of large
diameter and are provided with a very small number of
friction disks, or rings.

18. In Fig. 16 is shown a type of friction clutch in which
the disks have V-shaped circular corrugations that fit into
each other. The clutch is really a multiple-cone clutcli,
because the frictional surfaces are conical, each friction
member having two cone surfaces. One of these friction
rings is shown at a and another at 6. The space between
these two rings is occupied by the other rings (not shown)
of the series. In other respects, the clutch is similar to
multiple-disk clutches.

CONTRACTING AND EXPANDING CLUTCHES

19. There are some clutches that have cylindrical fric-
tion surfaces. One of the friction members is in the form

of a ring, or drum,
of fixed diameter,
and the other friction
member, or members,
press against either
the outer or the in-
ner surface of the
drum, or ring. When
the variable-diameter
member is outside the
fixed-diameter drum
and is drawn in
against the latter so
as to press the friction
surfaces together, the
clutch is generally
called a band clutch, or contracting clutch. If the variable-
diameter friction members are inside the clutch drum, the
clutch is generally called an expanding clutch.

Fio. 17

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§9

CONTROL MECHANISM

20. A modem contracting: clutch, is shown in Fig. 17.
In this clutch, the drum a is cast integral with the engine
fljrwheel b and is surrounded by two leather-faced steel bands c.
One end of each band is pivoted at d to the clutch member
that transmits the power to the driving wheels, and the other
end of each band is pivoted at e to levers /, having their
fulcrums at g on the driven clutch member. A sliding cone h
when pressed toward the flywheel b forces the long arms of
the levers / outwards in relation to the shaft axis, and the
levers therefore draw the bands c down on the drum a. When
the sliding cone h is
drawn away from the
fljrw^eel, the bands c
are released from the
drum a.

21. In Fig. 18 are
shown the principal
parts of an expand-
ing: clutcb.. In this
figure, the clutch
drum that is attached
to the fljnvheel of
the engine is shown
at a, and the clutch
shoes that bear
against the inner cylindrical surface of the drum when
the clutch is in engagement are shown at b and c.
One end of the shoe b is connected by a link d and a
pin ^ to a lever arm /, which, in turn, is pivotally con-
nected to an arm g b}'- means of a pin h. The arm g is rigidly
connected to the driven shaft shown at the center of the
clutch. The opposite end of the shoe b is fastened to an
arm i, which is similar to the arm g. The shoe c is similarly
connected to a movable lever arm / and the rigid arm g.
If the ends k and / of the levers / and j are separated by
moving them out radially from the clutch shaft, the shoes
b and c will be forced into engagement with the chitch drum.

222—19

Fio. 18

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TRANSMISSION AND

§9

In the complete clutch, this movement of the arms / and ;
is accomplished by means of a tapering sleeve, or cone, that
fits on the shaft. The nose of this sleeve is forced between
the ends k and / by means of a spring, which normally holds
the clutch in engagement. The clutch is released by with-
drawing the taper sleeve from under the ends of the lever
arms.

When a clutch of the form shown in Fig. 18 is rotating, the
centrifugal action tends to throw both the shoes and the
levers outwards from the center of the clutch and thus increase

the pressure between the
friction surfaces. At high
speeds, this increase of
pressure due to the cen-
trifugal force may become
great enough to make the
clutch hold much tighter
than it will at slow speed
of rotation. Whether this
is a desirable feature or
not does not seem to be
agreed upon among manu-
facturers who use expan-
sion clutches. In any case,
some means, such as
springs, must be provided,
so that, when the taper
sleeve is withdrawn to
release the clutch, the
shoes will be brought away
from the drum and there will be no contact between them no
matter how high may be the speed of rotation of the driven
shaft at the time of release.

It is, of course, possible to construct a clutch of this type
so that the centrifugal action on the levers will either tend
to draw the shoes away from the drum or at least balance
the tendency of the shoes to move out radially on accotmt
of the centrifugal force.

Fio. 19

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§ 9 CONTROL MECHANISM 19

22. A type of expanding clutch, which at first sight has
the appearance of a cone clutch, is shown in Fig. 19. The
fljrwheel a is connected to the end of the engine shaft b in the
usual manner, and is bored out to a cylindrical surface on the
side opposite the end of the engine shaft, so as to receive an
expansion ring c. The outer surface of the expansion ring is
cylindrical, and its inner surface is conical. This expansion
ring is forced out radially by the cone d when the latter is
pressed in toward the engine shaft b by the expansive action
of the coiled spring e. The expansion ring c is connected to
the cone d by means of bolts, one of which is shown near the
bottom of the illustration. This connection is made so that
the cone can slip into the expansion ring and out of it, but
there can be no rotation between these parts. A ball thrust
bearing is provided at /. The power is transmitted to the
parts back of the clutch by means of a jaw coupling, one
jaw of which is shown at g.

FRICTION MATERIAX.S FOR CLUTCHES

23. If one friction member of a clutch is of metal, the
following materials are commonly used for the other friction
member: Leather; cotton belting well saturated with oil
and some paint or pigment; camel's-hair fabric; vulcanized
wood fiber, also called fiber board; and cork inserted .into
dovetailed recesses in one of the friction members.

When metal is used on any of these materials, no lubrication
of the rubbing surfaces is required ; in fact, the presence of a
lubricant between these surfaces is generally injurious and
detrimental to the operation of the clutch. There are con-
ditions, however, under which a very small amount of certain
kinds of oil will act beneficially on friction surfaces that are
not in proper working condition.

The friction disks of multiple-disk clutches, when entirely
of metal, as is usually the case, are ordinarily of steel, or one
set of disks is of steel and the other set of bronze. In the
former case, the friction surfaces, of course, are steel on steel,
and in the latter case, bronze on steel. The disks are generally

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20 TRANSMISSION AND § 9

made of steel, hardened and tempered. The steel used to a
considerable extent for the disks of friction clutches is of the
same quality as that used in common wood saws.

In case of expanding or contracting clutches, one of the
friction surfaces is sometimes either cast-iron or steel casting,
and the other is brass or bronze.

SPEED-CHANGING MECHANISM

PURPOSE

24. Since the gasoline engine will give its highest eflS-
ciency when working with full charges, it should preferably
be operated under that condition as much as possible. Slight
changes of speed of the automobile and of the power of the
engine can be made by throttling and by manipulating the
spark; but for great speed changes, it is necessary to change
the gear ratio between the engine and the driving wheels.
The device used for this purpose is properly called a cliange-
speed grear, but, popularly, it is known as a transmts-
sion. As the gasoline engine applied to automobiles is
irreversible, it is necessary, in order to go backwards, to
change the direction of rotation of the driving wheels by
bringing into action a set of gear-wheels that will do this.
This set of gear-wheels is called the reversing gear, or
reverse for short, and in practically all modem transmissions
is incorporated in the change-speed gear.

Change-speed gears may be divided into four general classes,
namely, sliding change-speed gears, planetary change-speed
gears, individual-clutch change-speed gears, and friction gears
or transmissions,

SLIDING CHANGE-SPEBD GEARS

25. Sliding: cliange-speed grears are constructed
in two general types, one of which is known as the selective
transmission, and the other as the progressive transmission.
In the selective transmission, the change can be

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§ 9 CONTROL MECHANISM 21

made from any speed to any other while the car is traveling,
as from slow speed to high speed; but in the ppogpresslve
transmission, the change from slow to high speed, as
well as from high to slow speed, must be made step by step
through all the speeds.

There are two types of selective and progressive transmis-
sions, namely, the horizontal and the vertical. In the so-called
horizontal transmission the two shafts on which the change-
speed gears are mounted lie in the same horizontal plane,
while with the vertical transmission the shafts He in a ver-
tical plane, one above the other.

26, A horizontal tliree-speed and reverse slidingr-
gear progrressive changro-speed meclianisni, forming
part of the system for transmitting power from the engine
to the road wheels, is shown in Figs. 20 to 23. This device
gives three speeds forward and one reverse. The coupling a
at the front end connects to the driven side ot the fric-
tion clutch, which receives power from the engine. This
coupling is rigidly connected to the short shaft b and the
pinion gear e. The shaft d is in line with b and carries the
fork c of another coupling, by means of which connection is
made to the propeller shaft through which power is trans-
mitted to the rear axle. The shafts b and d, as illustrated,
are separated just back of the pinion e. In the actual con-
struction, one of these shafts is bored and the other extends
into it so that they are kept in line. The gears / and g are
connected by a sleeve, so as to form one rigid part that is
free to slide, but not to rotate, on the shaft d. This shaft
has two feathers, shown at the sides, that fit into corre-
sponding kejrways in the sleeve connecting the sliding gears
/ and g. At the front end of this pair of sliding gears are the
jaws of one side of a jaw clutch; the corresponding jaws of
the other side of the clutch are at the rear end of the shaft b
and form part of the pinion e. A side shaft, or back-gear
shaft, h lies parallel to the shafts b and d and carries the gears
i, y, k, and /. The first three of these gears are rigidly fastened
to the shaft A, but / is mounted on the shaft h so that it can

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TRANSMISSION AND

§9

slide, but not rotate, on it. Beneath the gear k is shown part
of an idler gear w that runs on a short shaft of its own. The
brake drum n just forward of the coupling fork c needs no
consideration in tracing out the action of the change-speed
gears.

27. In Fig. 20, the change-speed gears are set for slow
speed forward, or first speed. When in this position, the
pinion e drives the gear /, together with the shaft h and the
pinion ;; the pinion in turn drives the gear g and the shaft d
to which the coupling fork c is attached. The gear / on the

fwi cm

Fio. 20

side shaft is larger than the pinion e, and therefore rotates at
a slower speed. The speed of the pinion ; is, of course, the
same as that of /. The gear g, which is driven by the pinion /,
is larger than this pinion and consequently rotates at a slower
speed, which is the same as that of the shaft d and the fork c.
There are therefore two steps in the reduction of speed
between the coupling a and the fork c. The first reduction
of speed is between the pinion e and the side gear /, and the
second reduction is between the pinion / and the gear g.
Both the driving shaft b and the driven shaft d rotate in the
same direction.

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CONTROL MECHANISM

28. In Fig. 21, the gears are set for the second speed,
which in this case happens to be the intermediate forward
speed, because the mechanism gives three forward speeds.
This setting is secured by sliding the two gears / and g,
together with their connecting sleeve, forwards on the shaft d
from the position shown in Fig. 20. The side shaft is driven
at the same speed as before by means of the pinion e and the
gear /. The gear i on the side shaft drives the pinion / on the
shaft that carries part of the rear coupling. The gear i is
larger than the gear /; therefore, the latter gear rotates at a

Fio. 21

speed higher than the gear of the side shaft. There is a reduc-
tion of speed from the pinion e to the gear /, and an increase of
speed from the side shaft to the driven shaft that carries the
fork of the rear coupling. The result is that the rear shaft
rotates at a slower speed than the driving shaft b.

29. In Fig. 22, the gears are set for high speed forward,
or third speed. This setting is accomplished by sliding the
gears / and g forwards so that the clutch jaws at the front
end of the gear / engage with those on the rear end of the
pinion e. The transmission of power is now direct from the

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TRANSMISSION AND

§9

forward shaft b through the jaw clutch to the rear shaft d and
the fork that it carries at the back end. In changing to high
speed forward, the side gear / has been shifted forwards along
its shaft by means of mechanism not shown, so as to throw it
out of mesh with the pinion e. There is therefore no connec-
tion between the side shaft and the rotating parts of the
mechanism, and for this reason the side shaft and its gears
stand idle on the high-speed drive. This feature is not
essential to the operation of the device, and many change-
speed gears are not provided with the means of stopping the
rotation of the side gears in this manner.

Fio. 22

30, The reversing position of the speed-changing gears is
shown in Fig. 23. The side gear / is again in mesh with the
driving pinion e, and the sliding gear g has been moved to the
extreme rear position, so that it meshes with the idler gear m
under the pinion k. This pinion is small enough in diameter
to clear the gear g, and it engages with the idler gear w. The
side shaft is driven by the pinion e acting on the gear /, and
the pinion k drives the gear g by means of the idler gear m.
The introduction of this idler gear causes the gear g to revolve
in the same direction as the pinion fe, which direction is oppo-

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§9

CONTROL MECHANISM

site that of the shaft b and the driving pinion e. In all the
other cases that have been considered, the driving shaft b
and the driven shaft d rotate in the same direction for forward
travel of the car.

31. A foup-speed and reverse selective change-
speed drive is shown in Fig. 24. The coupling a at the
front end of the shaft receives power from the friction clutch.
At b is shown part of the rear coupling that transmits the
power to the rear axle by means of suitable connections.
The part b is mounted on a fluted shaft c whose forward end,

Fig. 23

reduced in diameter, is a running fit in the short sleeve that
connects the forward coupling a to the driving pinion d. The
side shaft e has rigidly attached to it five gears /, g, /t, i, and ;.
The shaft c carries two sliding members. One sliding member
consists of the gears k and /, which are rigidly fastened to a
connecting sleeve fluted to fit the shaft. The other sliding
member consists of a gear m from whose forward end, or side,
project the jaws of half a jaw coupling. The jaws of the other
half of the coupling are on the rear end of the driving pinion d.
An idler gear, which is brought into operation for reversing
the travel of the car, is partly shown at n.

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§ 9 CONTROL MECHANISM 27

The sliding parts are shown in their neutral positions.
When thus set, no power can be transmitted through the
change gears, even if the pinion d is revolving. The pinion d
always engages with the gear / on the side shaft, so that the
latter always rotates when the coupling a and pinion d are
running. Only one sliding member is moved at a time from
its neutral position. It is brought back to neutral position
before the other sliding member is moved.

32. For the -first speed forward, the gears k and /, both
mounted on the same sliding sleeve, are moved back so that
gear / meshes with gear i. The gear i on the side shaft e then
drives the shaft c by me^s of the gear /. For second speed
forward, the gears k and / are moved toward the front tmtil
gear k meshes with gear A. For third speed forward, gears k
and / are set in their neutral positions and the gear m is
moved back to engage with the gear g. High speed forward
is obtained by moving the gear m forwards so that the jaws
on its front end engage with their mating jaws on the pinion d.
The latter setting gives a direct drive from coupling a to
coupling b without the use of any gears, although, a:s already
stated, the gears d and / remain in mesh and the side shaft e
continues to rotate, but only idly. For backward travel of the
car, the gears k and / are moved back until the gear / meshes
with the idler gear n, which is driven by the pinion /.

The sliding gears k and / are shifted by means of the arm o
and the shifting bar p. The gear m and the sliding part of
the jaw clutch are shifted by the arm q and the shifter bar r.
Each of these shifter arms is rigidly connected to its own bar
and has a yoke that fits into a groove in the sliding member
that it shifts. Each of the shifter bars has a number of
depressions, or shallow holes, into which a steel ball is forced
part way by a spring so as to lock the shifter bar in the posi-
tion corresponding to the setting of the sliding gears. These
balls are in vertical holes at 5 and t. The depressions are
marked 1,2,3, 4, and R in the figure so as to correspond
with the first, second, third, and fourth forward speeds and
the reverse.

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§ 9 CONTROL MECHANISM 29

Of course, only one of the shifter bars is moved at a time.
This is accomplished by means of a speed-control lever, which
can be moved sidewise so as to engage with either of the shifter
bars.

33. In the speed-change mechanism illustrated in Fig. 25,
the control lever is shown at a. Both sliding bars are shown
in the end view at b and c, but only the bar c appears in the
side view, because b lies immediately back of it. The speed-
control lever a is fastened to a tubular shaft d that carries an
arm e at the end next to the shifting bars. This arm is shown
in the side view in engagement with the shifter bar c. The
tubular shaft d can be slid toward the right from the position
shown in the end view, so as to disengage the arm e from
the shifter bar b and bring it into engagement with the
shifter bar c, or as shown in the side view. The control
lever a moves in slots in a quandrant /. These slots are so
placed that the lever a can be pushed forwards or drawn back
only when it is in full engagement with one of the shifter
bars. The extent of the movement of the control lever is
restricted by the length of the slots in the quadrant. Thus,
when the lever is thrown either full forward or back, the
gears with which it is then in connection are set to the proper
position for the corresponding speed.

There are two slots in the quadrant in which the control
lever moves when shifting the gears. When the lever is near
the middle of either slot, the gears are in neutral position.
The two slots are connected by an opening — corresponding to
the neutral position of the lever — so that the lever can be
shifted sidewise to engage either of the sliding bars when the
gears are in neutral position. The two slots and the opening
between them together appear much like the letter H. One
of the slots is elongated and is provided with a stop that
ordinarily prevents the control lever from going more than the
proper distance to set the gears on slow speed forward. In
order to bring the control lever to the reverse position, it is
necessary to press down the push button g at the top of the
control lever. This allows the lever to move far enough to

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§ 9 CONTROL MECHANISM 31

bring the reverse gears into engagement. The stop men-
tioned is useful, as it prevents the reverse gears from being
thrown into action accidentally when shifting the gears
during forward travel of the car.

INDITIDUAI/-CL.UTCH CHANGJB-8PBBD GSABS

34. In the Indlvldual-clutcli system there is a
separate friction clutch for each speed. In Fig. 26 is shown
a system with two forward speeds and one reverse. The
flywheel a is keyed to the engine shaft and is connected to the
shaft b by the coupling c. From the shaft 6, motion is trans-
mitted to the propeller shaft d through the different clutches
and gears. Keyed to the shaft b are the gears e and / and
the friction cones g and h. The gear i and the clutch cone /
are parts of the same piece, which is provided with a bush-
ing k that fits loosely on the shaft b and is free to rotate on
the shaft. The collar / is loose on the shaft b and can be
moved by the lever m so as to force the end of the dog n
against the friction plate o and thus force the pin./? against
the cone g.

On the lay shaft q is keyed the gear r, but the gears 5 and t,
which are provided with bushings, fit loosely on the shaft.
The friction cones u and v are keyed to the shaft q, as are
also the friction disks w and x. The collar y also fits loosely
on the shaft q and operates on the dogs z and z^, throwing one
or the other of them against its friction disk and putting
the corresponding gear into operation. There is a small idle
gear that stands behind but meshes with the gears / and e,
which do not mesh with each other. There is also a brake
band at a^ that may be used to prevent the gear * and the
cone / from turning, or to bring the moving parts to rest.

35. In the position shown in Fig. 26, the collar / has
pushed out the long end of the dog n and forced the plate o
iagainst the pin />, causing it to force the cone g into the gear i
and the clutch disk ; on the cone h, thus locking the shafts b
and d together. Consequently, the propeller shaft turns

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TRANSMISSION AND

§9

with the same speed as the engine itself, which is the highest
speed that is transmitted. When the collar / releases the
dog n, the cones g and h are disengaged by the pressure of the
small springs shown in the hubs of these cones.

When a slow forward speed is desired, the collar y is forced
to the right, moving out the long arm of the dog z^, forcing
the friction, disk x against the gear 5 and the gear- against the
cone V. Consequently, motion is transmitted from the shaft b
to the shaft q by the gears / and 5 and the friction clutch v.
From the shaft q, motion is transmitted by the gear r to the
gear i and thence to the shaft d.

The individual-clutch system has not come into extensive
use, apparently on account of the difficulties found in keep-
ing the clutches in proper condition as to gripping sufficiently
without jerking and releasing without drag.

PLANETARY CHANGB-SPEED GEARS

36. The gear system of a tuvo speed and reverse
planetary transmission is illustrated in Fig. 27. One head

Fio. 27

of the gear-case and two of the planetary gears are shown
removed from the other parts. The driving pinion a is

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§ 9 CONTROL MECHANISM 33

rigidly fastened to the engine shaft 6, and the gear i is rigidly
attached to the drum / by means of a sleeve, which is free,
however, to turn on the engine shaft. The drum k has a web,
or head, that runs on the outside of the sleeve that forms part
of the drum /. The head of the drum k carries six studs on
which the gears c, d, e, /, g, and h are mounted and are free to
rotate. The studs that support the removed planetary gears d
and / are shown in place. An internal gear / is connected
rigidly to the sprocket wheel m by means of a flanged sleeve
that is free to run on the engine shaft, and on which the dust
cover n is supported so as to be free to rotate. This dust
cover is rigidly fastened to the drum k by screws when the
mechanism is completely assembled. The sprocket wheel
drives the chain for transmitting the power to the car axle.

The planetary gears are in three pairs that are alike and
perform similar service. The action of the transmission can
therefore be explained with reference to only one pair of the
planetary gears; gears c and h will therefore be used for this
purpose.

The coaxial gears a and i are some distance apart; c meshes
with a and extends some distance back of a; and h meshes
with i and extends forwards from i, so as to mesh with c.
The internal gear / also meshes with c,

37. The reverse motion will be explained first, because it
is simpler to describe than the slow speed forward. If the
drum k is prevented from rotating while the engine is running,
the stud that supports c will be held stationary so far as
rotation about the engine shaft b is concerned. The pinion a
then drives gear c, and this gear in turn drives the internal
gear / in a direction of rotation opposite that of the engine.
This will drive the car backwards in the ordinary arrangement
of the transmission system, which is such that the road wheels
rotate in the same direction as the engine shaft.

The gear i and drum / are driven so as to rotate idly during
the reverse motion.

Slow speed forward is obtained by holding the drum / so that
it cannot rotate; this also prevents rotation of the gear ♦.

222-20

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34 TRANSMISSION AND § 9

The driving pinion a then drives the planetary gear c, which
in turn drives the gear h. The rotation of the gear h on its
stud is in the same direction as that of the engine. Since the
gear h engages with the gear i, which is held stationary, it
must travel around the gear i in the same direction that the
engine rotates ; thus, it carries with it the stud on which it is
mounted. This stud in turn drives the web to which all the
studs are fastened; the gear c also must therefore swing
around the engine shaft, and since it engages with the internal
gear /, the latter is carried around in the direction of the
rotation of the engine, but at a slower speed.

For high speed forward, a friction clutch, not shown, that
lies just back of the drum / is brought into action. The flange
of this clutch is keyed to the engine shaft b in such a way as to
slide on it. When the clutch disk is pressed against the
drum y, this member and the gear i on it are gripped so as to
be driven by the engine shaft. The whole mechanism is thus
locked together and rotates as a unit without any relative
motion of the gears. This drives the sprocket wheel at the
same speed as that of the engine, and of course in the same
direction.

38. As will be observed, the gears are enclosed so as to be
protected from dust and dirt and at the same time retain a
lubricant.

When the car is standing and the engine running, all the
parts of the clutch move idly except the internal gear / and
the parts rigidly connected to it.

Contracting bands are used to grip the drums / and ^ so as
to prevent the rotation of one or the other, as desired. These
bands act like a friction clutch, and, when applied, allow the
car to pick up, or change, its speed gradually.

There are numerous modifications of planetary trans-
mission gears, some giving three forward speeds and a reverse.
A considerable number of cars of medium size, as well as light
cars, are successfully operated with planetary transmissions.

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CONTROL MECHANISM

FRICTION-GEAR TRANSMISSION

39< The simplest transmission that can be applied to an
automobile is the sO'Callerl frlettoii trtins*inifsHioii, of which
a typical example is illustrated in Fig. 28. In this trans-
missjon, the engine a is permanently attached to a disk b by
means of a shaft, A fricti<»n wheel c is mounted on a trans-
verse shaft d in such a manner that it can be made to move
across the face of the disk b from one side to the other and

drive the shaft d in any pt>sitiim. The friction wheel c is
shifted by a bell-crank e comiectetl to a crank / of the crmtrol
lever g, the bell -crank l>eiiig pivotctl to the left-sitle member of
the frame, not shown, at h. The bearings of the shaft d are
attached to the side members of the chassis frame in such
a manner that by pressure on the foot-pedal i the bearing's,
and hence the friction wheel t. can be brought forwards
into engagement with the disk b, when it will be il riven by
friction. As the lineal speed of points at different distances

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36 TRANSMISSION ANfD § 9

from the center of the disk b varies from zero at the center to
a maximum at the periphery, the rotative speed of the friction
wheel depends on its distance from the center of the disk b.
Thus, to obtain a slow speed, the friction wheel c is shifted
toward the center of the disk b by means of the control lever g;
and to obtain higher speeds, it is shifted toward the periphery.
In the position in which the friction wheel is shown, it is set
for the highest speed forward. To obtain a reverse, the
friction wheel is shifted past the center of the disk 6; then,
when brought into engagement by pressure on the pedal *, it
will drive the car backwards.

In the example presented, drive to the rear wheels is
supplied by a single chain, the front sprocket being attached
to the shaft d. The chain and sprockets are completely
enclosed in an oil-tight aluminiun housing ;.

As will be noticed, there is no clutch in the sense in which
that term is usually understood, the engine being clutched to
the driving mechanism by the friction wheel.

40. When constructed for a shaft drive to the rear wheels,
friction transmissions have a second disk placed at the rear of
the friction wheel. The axis of this disk is in line with that
of the first driving disk. The propeller shaft is then con-
nected to the shaft of the rear disk by a universal coupling.

41. A friction transmission of the bevel-roller type

is shown, mounted complete in a chassis, in Fig. 29. In this
transmission, the engine a drives a shaft b that carries at its
rear a driving cone c. This cone is mounted on the shaft b in
such a manner that it can move along that shaft, but must
rotate with it. A transverse shaft d carries on the left side
the forward speed bevel roller e, and on the right, the reverse
bevel roller /. Both bevel rollers can be moved sidewise on
the shaft d, which rotates with the rollers. Drive to the rear
axle is by chain g from a sprocket on the shaft d to a sprocket
on the differential h.

To change speed, the control lever i is moved; this move-
ment, through the medium of the bell-crank /, having its
fulcrum at fe, shifts the cones c and e simultaneously. It will

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ILJI

Pio. 29

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38 TRANSMISSION AND § 9

be understood that the nearer the cone e is brought to the
smaller end of the cone c, the smaller will be the rotative speed
of the shaft d, and vice versa, and hence of the driving wheels.
The cones c and e are brought into driving contact by appl5ang
pressure on the pedal /. This causes the contact lever m to
rotate around its fulcrum n, and the slotted link o carrying the
fulcrum k thus slides diagonally to the rear. This shifting
movement of the fulcrum k causes the rear end of the bell-
crank ] to swing toward the center of the car, thereby pressing
the cone e against the cone c. The car is driven backwards
by depressing the foot-pedal />, which act presses the roller /
against the cone c, the driving cone e having been previously
released.

ROPE TRANSMISSIONS

42. In a few light cars, each of the rear wheels is driven
by a rope that runs in the groove of a pulley, or sheave,
attached to the spokes of the wheel and also on a smaller
sheave mounted on a shaft that extends across the car and is
driven from the engine, generally by a chain. The inter-
mediate shaft, or jack-shaft, that drives the rope is mounted
in such a way that it can be moved with regard to its distance
from the driven wheels by a control lever. In order to stop
the car, the jack-shaft is moved backwards. This causes the
ropes to become so slack as to slip in the grooves and not
drive the wheels. To start the car, the jack-shaft is moved
forwards so as to tighten the ropes.

Chains having links covered with leather and made to fit
into the grooves of sheaves are also used to some extent for
transmitting power in the manner just mentioned.

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§ 9 CONTROL MECHANISM 39

POWER TRANSMISSION TO DRIVING WHEBIiS

UNlVBRSAIi COUPIilNGS

43. In an automobile fitted with a shaft-drive rear axle,
a flexible connection of some kind must be provided between
the propeller shaft and the gear-box, that is, the casing con-
taining the change-speed gears ; also, in many cases, such a
connection must be provided between the propeller shaft
and the rear axle. This flexible connection is needed to make
up for lack of alinement between the gear-box and rear axle,
due to the construction, and also for disturbance of alinement
due to play of the springs. For this purpose, so-called
universal coupling's, or Joints, are employed.

Pio. 30

A simple form of universal coupling is shown in Fig. 30.
In this figure, a may be taken as the shaft extending back
from the gear-box; 6, as the short shaft that carries a gear
that engages with the bevel gear on the differential of the
rear axle; and c, as the propeller shaft connecting the driving
shaft a and the driven shaft 6. The shafts a and c are con-
nected to a cross-shaped piece d that has rigid arms at right
angles, or perpendicular, to each other, the shafts a and c
being forked at the ends and having pin connections to d.
The rear shaft b is similarly connected to the cross e.

The coupling shown between the shafts a and c has the
peculiarity of not having a constant speed ratio of rotation;

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40 TRANSMISSION AND § 9

that is, if the shaft a is rotating at a uniform speed, the shaft c
^411 not rotate uniformly, but its speed will increase and then
decrease four times during each revolution. By the proper use
of a similar coupling between the shafts b and c, however, the
shaft b can be made to rotate at the same speed as the shaft a
during all parts of a revolution. In other words, the con-
nection between the shafts b and c can be made to counteract
the variable speed of the shaft c as produced by the connection
' between the shafts c and a. In order to do tljis, it is only
necessary that the forks on the shaft c shall lie in the same
plane This may be otherwise expressed by saying that
the shaft c must have such a form that if it is removed from
the crosses d and e and placed on the floor, it will lie flat.
It is also required that the shafts a and b make equal angles
witli the intermediate, or propeller, shaft c. This, of course,
is the case when the shafts a and b are parallel, as shown in
the illustration.

44, Since the distance between the gear-box and the rear
axle varies with the play of the rear springs, it is necessary on
a propeller-shaft drive to provide for this variation. In
practice this is done by leaving one member of one of the
universal couplings free to slide in the direction of the length
of the propeller shaft. Sometimes the sliding end of the
prij|>eller shaft is squared and works in a square hole formed
in thi' hub of the universal-joint fork; in other cases, a feather
is let into the shaft and a corresponding keyway is cut into
the Inib of the fork.

Wlule two properly arranged universal joints on a propeller
shaft will give a uniform speed of rotation, the tendency of
automobile builders is more and more toward the use of only
a sin^Oe joint at thfe front end of the propeller shaft. This
practice answers very well where the engine crank-shaft and
glcar-lHDX driving shaft are placed nearly in line with the bevel
jiinion shaft of the rear axle, as it gives approximately a
straight-line drive.

45, In Fig. 31 is shown one of the most widely used forms
of uinversal joints. It consists of a cross a and two forks

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§9

CONTROL MECHANISM

b and c. The one fork, b in this instance, is intended to slide,
a keyway d being cut in its hub. The fork c is intended to be

Pig. 31

keyed firmly or brazed to the member of the driving mecha-
nism to which it is attached. The cross is connected to the
forks by long pins. The resemblance between the universal
coupling shown in Fig. 30 and the joints shown in Fig. 31 will
be noticed.

46. In Fig. 32 is shown probably the simplest universal
joint that can be devised. When well made and of ample
size, a joint of this type will wear surprisingly well. One of
the two members, as a, has a square straight hole, into which
fits the squared end of the other driving member b. The four
surfaces, as c, of the squared end are not flat, but are part of
a cylindrical surface, thus permitting members a and b to be
out of line. The joint permits axial movement of its members.

Like all single imiversal joints, the one shown in Fig. 32
cannot give a uniform speed of rotation to the driven mem-
ber when the center lines of the driving and driven members
are not in the same straight line.

.J&^fPi^

Pio. 32

47. In Fig. 33 is shown a modification of the joint illus-
trated in Fig. 32. The driving member a and the driven mem-

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TRANSMISSION AND

§9

ber b have squared ends, and are connected by a sleeve c
having two square, straight holes with the flat surfaces of the

Pig. 34

holes in line. This form of joint is sometimes used between
the engine and the gear-box. As it consists really of two
universal joints; it will transmit a uniform speed of rotation
as long as the center lines of the driving and driven shafts are
parallel.

48. The form of universal joint illustrated in Fig. 34 is
known as the Oldham couplingr* It consists of three mem-
bers, shown separated in order to make the construction clear.
Both the driving member a and the driven member b have
a groove cut across the face of the flange, and the connecting
member c has a rectangular projection on each face, the two
projections being at right angles to each other. The pro-
jections fit loosely into the grooves of the driving and driven
members. The Oldham coupling can be employed only where
difference of alinement is very small. Hence, in automobile

work, its use is con-
fined to making dri-
ving connections to
magnetos and connec-
tions between the en-
gine and the gear-
box.

49. In Fig. 35 is

shown a universal

^^° 3^ joint that has its

working parts thoroughly protected against the entrance of

dust and dirt, thereby insuring durability. The driving shaft a

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§9

CONTROL MECHANISM

carries a fork e having balls, as g, formed at its two ends ; the
driven shaft h carries the fork d, each end of which has a ball,
as /. The cross connecting the two forks has four cups in
which the balls of the forks fit, and is made in halves to permit
the parts to be assembled. The casings c and h are bolted to
the flanges of the cross, as shown. The interior of the casing
is intended to be filled with grease, so as to insure proper and
continuous lubrication.

DIFFERENTIAL. GEARS

50. Principles of Operation. — Differential gears are
composed of a set of four or more gears attached to the ends

Pio. 36

of two shafts that come together and are usually in line,
so that both will rotate in the same direction; but if either
meets with extra resistance, it may rotate more slowly than

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TRANSMISSION AND

§9

the other or may stop altogether. These gears are used on
the driving axles or countershafts of automobiles. The axle
or countershaft is made in two parts, with a gear on the end of
each part where the parts come together; other gears mesh
with both these axle or countershaft gears and are driven from
the engine by a sprocket and chain or by bevel gears and shaft.
These gears turn the axle or countershaft, but permit its two
parts to turn in respect to each other so as to allow the

Pig. 37

automobile to go around a comer without causing the wheels
to slide, or skid. The assembly of gears used for this purpose
is known as the differential g^ear, or, sometimes, as the
compensating or equalizing gear.

51. Spur-Gear Differential. — In Fig. 36 is shown
a spur-gear differential, the ends of the two shafts of
which carry the gears c and d. The sprocket wheel e is driven

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T^-^

m.'

§ 9 CONTROL MECHANISM 46

from the engine by a chain, and is in turn fastened to a gear-
case that carries a series of small gears /, g, arranged in four
pairs, each gear being mounted on its own axle. The two gears
of each pair mesh together, and one is in mesh with the gear c
while the other meshes with the gear d. By this arrangement,
both gears c and d are drawn in one direction, and yet they
may turn with respect to each other when the resistance to the
turning of one is greater than that of the other. When
the resistance to the movement of gears c and d is the same,
the four pairs of small gears /, g do not turn on their axles
but simply carry the gears c and d around together.

62. Bevel-Gear Differential. — The two parts to
a driving axle or countershaft may be permitted to turn inde-
pendently of each other by means of a bevel-gear differen-
tial, as shown in Fig. 37. In this case, the driving shaft
from the engine carries the bevel gear a that meshes with the
bevel gear b on the differential gear-case c. To the inside of
the gear-case are fastened a nimiber of bevel gears, as d, that
are permitted to turn on the studs that hold them to the gear-
case. These gears in turn mesh with the bevel gears e and /
on the ends of the half axles, or shafts. The principle on
which the bevel-gear differential works is exactly the same
as that on which the spur-gear differential works. When
both gears meet with the same resistance, the small bevel
gears d do not turn on their bearings ; but when the movement
of one of the gears ^ or/ is resisted more than that of the other,
it lags behind, causing the small bevel gears to turn on their
axles sufficiently to cause the resistance to be equalized.

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TRANSMISSION AND

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CONTROL MECHANISMS

STEERING MECHANISMS

ARRANGEMENT OF STEERING CONNECTIONS

63« When a car is traveling straight ahead, the wheels
stand in the position shown by the full lines in Fig. 38, which
is a diagrammatic outline of a top view of the frame, axles,
and wheels of an automobile. The axles of the wheels appear

Pio. 38

to be parallel to each other when looked at from above, as in
this view. If the car is to turn a curve whose center is at a,
the front wheels b and c must be swiveled about the more or
less vertical pivots d and e of their respective knuckle joints.

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§9

CONTROL MECHANISM

When turning toward the left, as indicated in the figure, the
left-hand front wheel b must swivel through a greater angle
than the right-hand front wheel, which is at the outer side of
the curve along which the car is traveling. The path that
the left-hand wheel follows is indicated by the arc / g whose
center is at a, and the path of the right-hand wheel is along
the arc h i, whose center is also at a. It is necessary for the
wheels to swivel to such an extent that their axes, if extended,
will intersect on an extension of the rear axle, as shown.

Fig. 39

The lines a d and a e represent extensions of the axes of the
front wheels. The angle through which the left-hand wheel
must be swiveled is shown at ;, and that through which the
right-hand wheel must be swiveled, at k. It can be readily
seen that the arc / for the left-hand, or inside, wheel is larger
than the arc k for the outside wheel c.

64. One of the two methods of connecting wheels together
to fulfil the conditions mentioned in Art. 53 is shown in
Fig. 39. The full lines indicate the position of the steering

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TRANSMISSION AND

§9

mechanism for the car to go straight ahead. The arms a
and b of the steering knuckles are connected by the distance
rod c. These arms a and b stand in such a position when the
car is going straight ahead that if a line is drawn through the
center of the swivel pin d of one of the knuckle joints and also
through the center of the pin connecting that arm to the
distance rod, and another line is similarly drawn through the
swivel pin e and the pin connecting the corresponding arm to
the distance rod, these two lines will intersect each other on
or near the center line of the axis common to the rear wheels,
as indicated at /. The length of the distance-rod arms a and b
on the steering knuckles is made such that when the wheels
are swung around to turn a curve, the wheels will take posi-

Fio. 40

tions in which their axes, if extended, would intersect on or
near an extension of the center line of the rear axle. The
intersection for this position is shown at g.

If the steering mechanism were mathematically correct
in its operation, then, for any position of the swiveled road
wheels, the intersection of the extended axes of the front
wheels would lie exactly on the extension of the rear axle.
The mechanism shown, however, does not exactly give this
result, but one that is near enough for all practical purposes.

56. Instead of placing the distance rod back of the front
axle, as shown in Figs. 39 and 40, it may be placed in front of
the front axle and the arms of the knuckles extended forwards

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§9

CONTROL MECHANISM

to engage with it, as shown in Fig. 41. This is the second of
the two methods that are almost universally used. In this
case, the distance between the ends of the steering-knuckle
arms is greater than the distance between the steering-
knuckle pins. The same condition exists as to the lines
through the steering-knuckle pivots and connections of the

Pig. 41

distance rod intersecting at or near the center of the rear axes.
One of the steering knuckles is provided with an arm to
which the reach rod leading to the steering gear is attached,
usually by means of a ball joint. This reach-rod arm a may
be either above the front axle, as in Fig. 40, or below it, as in
Fig. 41.

STEERING GEARS

66. steer ingr gr^ars may be broadly divided into tiller
steering gears and wheel steering gears. In a tiller steering:
grear, steering is effected by moving by hand a long lever,
which in turn is connected by suitable means to one of the
steering knuckles; this form of steering gear is now prac-
tically obsolete, being used only on some light electric vehicles.
In a wheel steering gear, as implied by the name, steering is
effected by turning a wheel, ranging in modem cars between
14 and 18 inches in diameter.

Steering gears may also be classified as reversible and
irreversible steering gears. When a simple form of mechanism
consisting of a lever arm rigidly attached to the lower end of

222—21

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TRANSMISSION AND

§9

the steering column is used, and the reach rod is attached
directly to the outer end of this arm, an obstruction striking
one of the road wheels will cause the hand steering wheel or
tiller to rotate and thus deflect the car from its direction of
travel, unless the steering wheel or tiller is very firmly gripped
by the hands of the driver, or locked in position by some
means not usually found in automobiles. A steering gear that
behaves in this manner is called a reversible steering:
grear. It is evident that the reason for the name is that it
is possible to rotate the hand wheel by force applied to one or

both of the road wheels.
A steering gear that can-
not readily be reversed
in this manner is called
an Irreversible steer-
ing g^ear. While none
of the steering gears in
actual use fully possess
this property of irre-
versibility when in good
working order, they are
usually referred to as
being irreversible when
but little effort at the
hand wheel is required
to keep the car from being deflected from its path when the
road wheels strike an obstruction.

57. In one of the simplest forms of a wheel steering gear,
a spur gear is mounted on an inclined shaft and at the base
of the steering column, the upper end of the shaft carrying the
steering wheel. A rack movable across the car meshes with
the spur gear and has one end connected by a reach rod
to the reach-rod arm of one steering knuckle.

In a modification of the steering gear just described, the
spur gear is replaced by a bevel pinion and the rack by a
segment of a bevel gear that carries a lever connected to one
of the steering knuckles by a reach rod.

Fio. 42

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§9

CONTROL MECHANISM

Both the rack-and-pinion type and the bevel-gear type
of steering gear are reversible, and hence are now seldom used.

58. Fig. 42 illustrates diagrammatically what is known as
the -worm-and-sector type of steering gear, which is the
type almost universally used in pleasure automobiles. Within
the steering column a is a steering shaft carrying at its k>wer
end the worm b meshing with a sector c of a wonn- wheel.
The worm b is confined longitudinally by thrust bearings,
but can be rotated by turning the steering ^heel d. The
shaft on which the sector c turns carries at one end the crank-
arm e that is connected
by the reach rod / to
the reach-rod arm g of
one of the steering
knuckles.

Rotation of the steer-
ing wheel causes the
worm b to rotate with it,
and the sector of the
worm-wheel is thus
made to rotate about
its own horizontal axis.
The lower end of the
crank e is thus swung
forwards or backwards
according to the direc-
tion of rotation of the
hand steering wheel.
The reach rod / is correspondingly moved forwards and back-
wards, so as to cause the knuckle joints to turn aljuut their
own swivel pins, and thus swing the road wheels, according,'
to the direction of rotation of the hand wheel.

59. Fig. 43 shows a design of a worm and wctrnvwlieil
used at the lower end of the steering column in whit h a t mii^
plete worm-wheel is used instead of only a sectnv The part
at the right side of the illustration shows half of the casi^
removed from its place.

Fig. 43

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TRANSMISSION AND

§9

The object of using a whole worm-wheel instead of a sector
of one is to provide for a long life; when the worm-wheel has
worn appreciably in one place, an unworn portion can be
brought into mesh with the worm, turning the crank-arm,
which fits over a squared end of the worm-wheel shaft, 90®.

60. In Fig. 44 is shown a form of irreversible steering
gear, known as the screw-and-nut steering grear, that

is used chiefly on trucks.
The steering shaft a is
threaded at the lower end,
and, while free to turn, is
confined longitudinally.
A nut b is fitted to the
threaded end of the shaft a
and has projections carry-
ing 'blocks c that rest in
slots of a forked bell-crank
d having its fulcrum at e.
Rotation of the steering
wheel / causes the nut b
to travel up or down, thus
* swinging the bell-crank d
around its fulcrum. A
reach rod leading to one of
the steering knuckles is
attached to the lower end g
of the bell-crank.

Steering gears of the
screw-and-nut type, like
the one shown, that have a
rather fine pitch of thread
are extremely powerful
and entirely irreversible, which makes them particularly suit-
able for the steering of heavy trucks moving at low speeds.
On the other hand, considerable rotation of the steering wheel
is required for changing the steering road wheels from straight
ahead to their extreme positions; this slow action renders

Fio. 44

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§9

CONTROL MECHANISM

their use objectionable in pleasure cars, which are designed to
run at higher speeds than trucks.

61. A quick-acting steering gear of the screw-and-nut
type, as used for pleasure cars, is shown in Fig. 45. The

Fio. 45

lower end of the steering column engages with two nuts a
and h by means of screw threads, one of which is right-handed
and the other left-handed. Thus, when the hand wheel is
rotated, the nuts a and b either approach or recede from each
other, both moving with the same speed.

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TRANSMISSION AND

§9

On the left-hand side of the nut a 'is an extension that
engages with a pin c that is carried by a part d which is
pivoted at e and rigidly connected to the crank /. The nut h
has a similar extension at its right-hand side that engages
with a pin g, which is also rigidly fastened to d and the part
carrying the crank /. The pins c and g are each at the same
distance from the swivel pin e. When the steering wheel is
rotated so as to cause the nut a to travel downwards and the
nut h upwards, the extension of a presses down on the pin c
to move the arm / forwards, or toward the right, as shown in
the figure. Since the nut h travels up at the same rate that
the nut a comes down, the two extensions from the nuts keep
in contact with the pins c and g, so that there is no oppor-
tunity for lost motion in the parts that carry the arm /.

Fig. 46

62. In order to prevent excessive shocks upon the steer-
ing mechanism, the reach rod and distance rod are sometimes
provided at one end with springs strong enough to hold the
steering mechanism in position under ordinary conditions,
but which give slightly if a large obstruction is struck on the
road. Such an arrangement is shown in Fig. 46. The arm a
has a ball h at its end against which press two bearing pieces c
and d that are held firmly against the ball 6 by means of coil
springs e and /. The nut g is screwed into the. end of the
tubular piece containing the springs and is held from jarring
loose by a cotter pin h. The nut g can be adjusted to regulate
the pressure against the ball h.

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§^^

CONTROL MECHANISM

BRAKE MECHANISM

CONTRACTING AND KXPANDING BRAKES

63. The brakes used in automobile practice are applied
either on the outside of a cylindrical brake drum and con-
tracted thereon by levers operated from a foot-pedal or hand-
brake lever, or they are applied on the inside of the brake
drum and applied by expanding. If applied to the outside
of the brake drum, the brakes are called contracting:
brakes, and if applied to the inside, expanding^ brakes.
It is the usual practice to fit two entirely separate sets of
brakes to automobiles. The one brake system is used in
ordinary service, and
is therefore called the
service brake.
The second brake sys-
tem is intended for
emergency use, and
hence the term emer-
gency brake is ap-
plied to it.

It was formerly the
common practice to
place the service
brake on some rota-
ting part of the speed-
changing mechanism,
or on a drum placed directly on the propeller shaft, and
to apply the emergency brakes to a drum fastened to each
rear wheel. The present tendency is to apply both sets of
brakes to drums bolted to the rear-wheel hubs, making
the one set contracting and the other expanding. In cars
having a single-chain drive, it is customary to apply one
braking system to the drum or drums of the differential,
in which case the brake bands are of the external con-
tracting type.

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56 TRANSMISSION AND § 9

64. A typical modem braking sjrstem, as applied to a
drum bolted to the hub of a rear wheel, is shown in Fig. 47.
In this illustration, for the sake of clearness, neither the rear
wheel nor the brake drum is shown. The external brake
band a is made of spring steel lined with a material that
has a high coefficient of friction and is attached by copper
rivets.

Each end of the brake band a is attached by pins, as b and c,
to a short lever keyed at its center to the brake shaft d. This
shaft is free to turn in a stationary bearing e that forms part
of the rear-axle housing. The brake lever / is also keyed
to the brake shaft d, and is connected by a rod (not shown)
either to a hand lever or a foot-pedal. It will be seen that if
the brake lever / is pulled forwards, that is, in the direction
of the arrow, the pin c will move upwards and the pin b down-
wards, thereby shortening the brake band and contracting it
on the drum.

In the best modem practice, the brake band a is confined
sidewise by hooks g attached to the rear-axle housing.
To prevent the brake band from coming into contact with
the brake drum when not in use, or dragging, as it is
usually called, and thereby unnecessarily reducing the speed
of the car, it is becoming universal practice to suspend the
brake band from a stationary part of the rear-axle housing
by a spring hooked into the eye h.

The internal brake consists of two shoes i and / pivoted at k
to the rear-axle housing. These shoes, which in this instance
are of bronze with cork inserted in pockets, can be pressed
outwards against the inside of the brake drum by puUing for-
wards on a lever arm attached to the short shaft carrying the
lever /, from the ends of which extend the links m and n to the
free ends of the brake shoes. A strong helical spring o pre-
vents the brake shoes from rattling.

Both brakes here shown are double acting, by which is meant
that they work equally well when backing as when going
ahead. Some of the earliest cars were fitted with brakes that
would hold only when going ahead. Such brakes are called
single acting, but are now obsolete.

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§ 9 CONTROL MECHANISM 57

65. Brake drums are made of cast iron, bronze, cast
steel, and pressed steel. For the lining of brake bands,
leather, fiber, and a fabric called cameV s-hair belting were
formerly used quite extensively; these materials have a high
coeflScient of friction, but are very liable to char through
overheating due to descending long and steep hills with the
brakes holding the car in check. When the lining chars, the
brakes are worthless until repaired. This defect of the mate-
rials named has led to the production of brake linings com-
posed chiefly of asbestos and copper or brass wire cloth of
close mesh, which do not char under heat, and are claimed not
to be affected by oil or grease.

The brake shoes of internal expanding brakes are usually
made of bronze, and bear directly against the brake drums,
the brake shoes being lined with material that is easily
removed and replaced when worn.

66. The tendency of brake drums is to wear in such a
manner as to form a series of concentric grooves. When thus
worn, new linings applied to brake bands or brake shoes will
be rapidly cut out. If the drum is still thick enough, it should
be bored or turned, as the case may be, in a lathe ; if not thick
enough, the drum should be replaced by a new one.

BRAKE EQUALIZERS

67. Unless some means are provided for keeping the ten-
sion equal in the two rods that connect to the shoes of a pair
of hub brakes, one of the shoes, when applying the brakes,
will bear against its drum harder than the other if the adjust-
ment is not perfectly the same for each brake. Such adjust-
ment is difficult to obtain, and even then it will not generally
continue as the brakes wear in service. When one hub
brake grips harder than its mate, there is a tendency to slew
the car arotmd toward the side whose brake has the weaker

grip-
Various forms of brake equalizers are used to obtain
equal force of application for a pair of hub brakes. Probably

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58 CONTROL MECHANISM § 9

the simplest form of equalizers is a bar extending across the
car, and having connection at each end to one of the tension
rods that runs back to the brake shoes; also connection at the
middle of the bar to the rod that connects to the brake pedal
or hand lever by means of which the driver applies the brake.
The pull on the rods leading from the brake shoes will, of
course, be the same in each with this arrangement. Another
device consists of separate crank-shafts, one for each brake
shoe, placed in line with each other across the length of
the car. The crank-levers at the outer ends of the shafts
are connected to the tension rods that run back to the brakes,
and the crank-levers at the adjacent inner ends of the divided
shaft are connected to a short equalizer bar in the same man-
ner as just described when the bar extends completely across
the car. Sometimes, however, instead of using a short
equalizer bar in connection with the pair of crank-shafts, a
pulley is used and a chain or cable passes aroimd it and con-
nects to the adjacent cranks of the two shafts.

Even with a brake equalizer of the most effective form,
the resistance that a pair of hub brakes offers to the rotation
of the wheels is not the same, unless the coefficient of friction
between the rubbing surfaces of the brake shoe and drum
is the same in each case. Thus, if one brake is dry and the
other oily, they will not grip the wheels so as to resist the
rotation of each wheel with equal force, even though the pres-
sure of the shoe against the drum is the same for each brake.

The introduction of an equalizer in the brake system is
somewhat dangerous imless special precautions in the design
of the equalizer system are taken. This danger is, that if
one of the rods leading from a brake shoe is broken, then the
other brake becomes inoperative, unless the motion of the
equalizing device is so restricted that the service brake can
be applied by additional motion of the pedal or hand lever.

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BEARINGS AND LUBRICATION

BEARINGS

TYPES OF BEARINGS

1. The oldest and simplest form of bearing used in
automobile-engine practice is the plain bearing, in which the
journal of the shaft fits in a sleeve called the bearing, or box,
and touches the supporting surface along its entire length.
In roller bearings , rollers are interposed between the bearing
and the journal, thus reducing the bearing surface and having
rolling instead of sliding friction. In ball bearings, a number
of balls surround the journal and lie between it and the
bearing proper. Each ball thus touches the journal and
the bearing surface in single points, instead of along lines.
There is rolling friction, however, and the frictional resist-
ance is much less than in ordinary bearings. . •

SHAFT BEARINGS

2. Defii^itions. — A plain sliaft bearing: in its simplest
form consists of a journal and a box. The Journal is a
cylindrical part, such as a portion of a shaft, whose convex
surface bears against and is free to rotate in the hollow
cylindrical part, called the box. The box may be in one
piece or it may be divided into two or more parts. Such
division is made for convenience in assembling the bearing
and taking it apart, and also for making adjustments for

OOrrmOHTCD by international textbook company. ENTKREO at •TATIONBRf HALL. LONDON

§10

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BEARINGS AND LUBRICATION

§10

taking up wear and securing a proper fit. Either the journal
or the box may rotate.

A lining^ is very often used between the journal and the
main body of the box. The object of using the lining is to
provide a more suitable material for the journal to rub
against than that which is used for the supporting parts or
frame of the machine, or to provide a ready means of repla-
cing a worn part.

3. Fig. 1 shows a plain shaft bearing in which the box
is split. Both the end view of the bearing and the longi-
tudinal sectional view of the box with the journal in place are
shown. In this figure, the journal is indicated at a; the main
body of the box, which may be part of the frame of the
machine, at b ; the cap, at c; and the lining, in two parts, which

Fic. 1

are almost complete half cylinders, at d. At e are shown fiat
plates of metal interposed between the cap and body of the
bearing. These plates are clamped rigidly together by the
capscrews /. The plates e extend in between the two parts
of the sleeve, or lining, and prevent the rotation of the lining
with the journal. The shoulders g hold the cap in position
so that it cannot move sidewise relatively to the journal.
The linings must be held in some way so that they can neither
move endwise nor rotate. In the center of the linings, as
shown in the right-hand view, pins are sometimes used to
prevent any movement of the linings.- In vertical engines
used on automobiles, the crank-shaft, or main shaft, is often
supported by bearings of this nature. These, however, are
generally turned upside down from the position shown in
the figure, so that the cap is at the bottom.

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§ 10 BEARINGS AND LUBRICATION 3

4. Materials for Sliaft Bearing^s. — The journal,
since it is a part of the shaft, is generally made of steel.
The kind of metal used for the portion of the box against
which the journal runs depends on the speed and pressure
tmder which the bearings must operate. When both the
speed and the pressure are high, usually some such material
as brass, bronze, or oije of the * 'white metals," which include
Babbitt metal, is used. These materials offer less frictional
resistance to the rotation of the parts relative to each other,
and are less liable to abrade, cut, and seize than when the
materials such as are found ordinarily in the frames of
machines are used for one of the bearing surfaces. The
mateHals used in the frames are usually cast iron, steel, and
aluminum alloy.

5. Brass is an alloy composed chiefly of copper and
zinc, although a very small quantity of other materials, such
as lead and tin, is frequently added. Brass varies in color
from bright yellow to a dark copper color, according to
whether a large or a small quantity of the zinc and other
metals than copper is used. The alloy may be either very
soft or quite hard, according to the proportion of the materials
that cause hardness.

Bronze is an alloy composed chiefly of copper, tin, and lead.
In the bearing qualities of bronze the copper largely pre-
dominates. Zinc is also frequently present, and sometimes
a small quantity of phosphorus is found in the alloy.

The TvMte metals , including Babbitt, are of a whitish
color, resembling that of tin or solder. These alloys are
softer than brass, but are weak, and are therefore used only
as linings in the box of the bearing.

Whether brass and bronze are used as a lining or to make
up the entire box depends chiefly on the size and form of
the box. Except when the box is very small and not compli-
cated, it is generally cheaper and advisable to use brass or
bronze as a lining only. The antifriction qualities of Babbitt,
as well as the ease with which the boxes may be lined with it,
make it a very common bearing material.

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BEARINGS AND LUBRICATION

When the pressure between the bearing surfaces is light
and there is almost absolute certainty of lubrication, even
though the bearing may be neglected to a considerable extent,
cast iron makes an excellent bearing surface for a steel journal.
If, however, cutting and abrasion ever begin, there will
generally be almost instant seizure of the parts, so that there
can be no further rotation between them. The injury done
to the box and journal in such a case is generally severe,
except when there is only a slight amount of turning force
acting to rotate the one relatively to the other.

6. Oil Grooves. — Generally, oil g^rooves are cut in

the surface of the bearing against which the journal rotates.
It is usually advisable to cut these grooves where the pressure
between the journal and the lining of the box is least. If

the oil groove is cut where the
pressure is highest, its edges will
have a tendency to scrape the
oil from the journal and thus
prevent efficient lubrication. If
a box has such a groove in it,
this objectionable action can be
eliminated to some extent by
beveling off the edges of the
groove. The bevel should ex-
tend well back from the groove,
but not down very far into it.

7. Oil 8coop. — The cap b
on the lower end of the connect-
ing-rod, Fig. 2, has an oil
scoop a for picking up oil for the crankpin bearing. The
rapid motion of the scoop through the oil in the bottom
of the crank-case causes some of the oil to flow up through
the oilway d and oil grooves e, cut in the lower brass c, to
the bearing surfaces. The movement of the connecting-rod
is in a direction that causes the open front of the scoop to
strike the oil.

Fio. 2

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§10

BEARINGS AND LUBRICATION

S. Sliims. — Some forms of connecting-rods are pro\-ided
with easy means of taking up wear on the bearings in the shape
of slilmsy or thiit strips of copper or brass, which are inter-
posed between the large end of the connecting-rod and the
bearing cap. The cap is bolted down tight against these
shims, and when the bearing becomes worn, one or more
shims are taken out on each side. Provided the bearing has
not been cut and is not badly worn out of shape» this will
take up the wear satisfactorih. Care should be taken that
there is not the slightest evidence of tightness or binding
after the bolts have been tightened. If the bearing is in
the slightest degree tight, it will squeeze the oil out and begin
to overheat and cut.

When bearings are set up too tightly, heating is inevitable,
and probably more hot bearings result from this cause than
from any other, and with less excuse. An attempt is often
•made to stop a knocking or pounding in an engine by setting
up the brasses when the pounding could and should be stopped
in some other way. The direct cause of heating of bearings
when the brasses are set up too tightly is the abnormal friction
that is produced by the pressure of the brasses on the journal.

9. Thmst Bearing. — A plain thrust bearliif^ for

preventing end motion of a shaft has the general appearance
of a plain journal bearing
with one or more collars ex-
tending out around it.
Such a thrust bearing is
shown in Fig. 3. The jour-
nal a has collars b that fit
in and press against cor-
responding grooves c in the box that surrounds the bearing,
By using a number of collars, as shown, the bearing surfaces
for resisting end thrust of the shaft c[in be made sufficiently
large to keep down the bearing pressure per unit area to a
suitable intensity without using collars of large diameter
relative to the diameter of the shaft- A collar at the end of
a journal bearing will prevent end motion in one direction*

vililalali

Fjo. 3

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BEARINGS AND LUBRICATION

§10

ROLLER BEARINGS

10. A roller bearingr has rollers interposed between
the journal and the supporting parts that correspond to the
box, or lining, of a plain shaft bearing. The rollers may be
either cylindrical or conical, according to the forms of the
surfaces on which they roll. The cylindrical rollers are
generally either solid round bars, such
as a piece of shafting, or they are
made up by rolling a flat or rectan-
gular strip of spring steel around a
cylinder, so as to form a hollow helix
whose outer cylindrical surface forms
the bearing part of the roller. The
conical rollers are usually made solid.

11. A cylindrical roller bear-
ing with sleeve rollers is shown
partly separated in Fig. 4. It con-
sists of an outer shell a, inside of
which the cage and rollers b rotate.
The sleeve c fits inside the cage and
rollers. The rollers are retained in
the cage, so as to hold them parallel
to the shaft that fits in the sleeve c.
The cage also prevents the rollers
from moving endwise to any great
extent.

12. Roller Tbrust Bearings.

A thrust bearing with conical rollers
is shown separated in Fig. 5. The
rollers a are arranged in a circle, with their smaller ends
pointed toward the center of the bearing, which corresponds
to the axis of the shaft. All the rollers are retained by
a cage 6. and roll on bearing plates c and d. These plates
have conical surfaces to correspond with the taper of the
rollers.

Fig. 4

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§ 10

BEARINGS AND LUBRICATION

13. A roller thrust bearing with cylindrical rollers is
shown in Fig. 6. The rollers are made very short, the length
of a roller being usually less than its diameter. Several of

the rollers are put in each radial slot of the cage, which
retains all the rollers. The illustration shows five short
rollers in each slot of the cage c. The ends of the rollers are
crowned so that they bear against each other only on very
small areas near the axis of the rollers. The bearing plates
are flat-sided rings, as shown at d and e. Bearings of this

Pio. 6

type will stand heavy service, but, compared with ball bear-
ings, they are generally too expensive to be considered,
especially in view of the fact that it is usually difficult to

222—22

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BEARINGS AND LUBRICATION

obtain, except from the one maker, new rollers to replace
worn or broken ones, whereas standard-sized balls can be
secured from dealers in all large cities and many towns.

14. Solid-Boiler Bearings. — An application of solid-
roller bearings to the transmission gear of an automo-
bile is shown in Fig. 7. The roller bearing shown at a
supports one end of the driving shaft b that transmits power
through the bevel gears c and d to the driving axle e. A

Fio. 7

second roller bearing is shown at / on the axle e, and at g
and h are shown roller thrust bearings for the purpose of
taking the thrust of the shafts and preventing end motion.
The gear-case i surrounds and protects the gears and bear-
ings, and should contain a liberal supply of grease or oil.

15. Conical-Roller Thrust Bearing:. — In Fig. 8 a
conical-roller thrust bearing is shown partly in sec-
tion. The taper rollers, one of which is shown at a, are

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§10

BEARINGS AND LUBRICATION

held in place by a cage consisting of two rings fastened
together with small rods. The outer surface of the sleeve,
or inner race, b on which the rollers run is tapered to suit
the rollers and has a couple of rings, or beads, that fit into
grooves in the rollers a to prevent end motion to any great
extent. The outer casing, or race, c has a plain conical
inside surface to fit the rollers, and is made of suitable form
outside to fit into the part that is to be supported.

A bearing of this form will take both side pressure of the
journal and end pressure in one direction. If a pair of such
bearings is used on the same shaft, with either the large or
the small ends of the two sets of rollers toward each other,
end thrust of the shaft in both
directions will be prevented.

16. Automobile Conical-
Boiler Bearings. — Several
conical-roller bearings as applied
to the main driving mechanism
of an automobile are shown in
Fig. 9. The driving shaft a is
supplied with two conical-roller
bearings b and c. They taper
in opposite directions, thus hold-
ing the shaft firmly in position
against any force that might
produce end motion. The cup d is threaded on the outside
to permit of adjusting the bearing for wear. The bevel
gears e and / transmit the power to the driving axles g and h
through the differential gears in the case i. The conical-
roller bearings / and k keep the axles in position, and are
provided with adjusting cups, as in the bearing at a. At
/ and m are shown similar conical-roller bearings between the
wheel hub n and the axle sleeve o. The inclination of these
bearings is such as to keep the hub in position without
providing a special thrust bearing.

17. Colled-BoUer Bearings. — In Fig. 10 is shown a
roller bearing in which the rollers are made by winding

Pio. 8

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§10

BEARINGS AND LUBRICATION

square or rectangular bars in much the same way that a
helical spring is made. The rollers are held in a cage formed
of rings a. These rings are held together by three connecting
pieces b that have projections c for retaining the rollers d.
The cage is made of brass and fits the rollers loosely, so as
to allow free movement without increasing the friction.

Fio. 10

The hollow form of the rollers enables them to take in oil
and distribute it, and the elasticity of the rollers enables them
to accommodate themselves to the surfaces on which they
roll. The inside casing is shown at e and the outside casing
at /, the rollers being in contact with both of these most of
the time.

BALL BEARINGS

18« In ball bearingfs, a number of balls are inter-
posed between the parts that rotate relatively to each other.
The bearings are constructed in various ways, either for
resisting side pressure or radial pressure of a journal against
its bearings, for resisting end thrust of the shaft, or for
resisting both radial pressure and end thrust combined.

19. A ciip-and-cone ball bearing is shown in section in
Fig. 11. The axis of the bearing is indicated by the line d e,
and the balls c run on the races a b. In this particular form
of bearings owing to the shape of the races, a is called the

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BEARINGS AND LUBRICATION

§ 10

Pio. 11

cup and b the cone. There are, of course, a number of balls
arranged in a ring, or circle. In some bearings, the balls
are not restrained in their motion otherwise than by the races;
but for heavy service, the balls are
generally retained in a cage that pre-
vents them from coming in contact
with and rubbing against each other.
The retainer is of great convenience in
preventing the balls from falling out
when the bearing is taken apart. Each
ball has only two points of contact with
the races; therefore, this form of bearing
is called a two-potnt-contact ball bearing.
The cone b can generally be adjusted
along the axis to provide for wear.

20. An annular ball bearing^ is

shown partly in sec-
tion in Fig. 12. The

center line is indicated by c I. The races

a and b may be considered as plain rings

slightly grooved to form a path for the

balls d. The radius of the groove in each

ring is slightly greater than that of the

balls. Bearings of this form are primarily

intended to resist radial, or side, pressure,

but when properly constructed they will

also resist a great deal of end thrust.

They are used extensively in automobiles.

When used in wheels, they successfully

resist the end thrust that comes on them

when the car is turning curves or is on

the sides of a crowned roadway.

There is no way of adjusting this form

of bearing to take up wear. When the

bearing is worn loose, its life is assumed to be finished,

and for this reason it is considered unnecessary to have

any means of adjusting the bearing. Of course, new

Fio. 12

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BEARINGS AND LUBRICATION

balls may be put in, and if balls large enough in diameter
are used, the wear may be taken up. As many balls are
inserted as can be put in before the inner and outer races
are brought into final concentric >- /y^: :; <

position relative to each other;
or the balls may be held at equal
distances apart, either by means
of a cage or by inserting springs
between them.

Fio. 13

21. A ball thrust bear-
ing is shown in section in Fig. 13.
Slightly grooved races a and b
form a path for the balls, which
are kept in place and prevented
from rubbing against each other
by means of a cage made of two flat
rings c. The rings of this cage are spaced by ferrules and are
rigidly held together by means of bolts or rivets. The race b
is spherically crowned on the surface e, where it is supported
by the frame of the machine so that it can readily adjust
itself to any springing or lack of alinement of the shaft that
carries the race a. This spherical crowned surface is exag-
gerated in this figure in order to show it plainly. This provi-
sion for adjustment is extremely important in a ball bearing
that receives considerable end thrust, as it permits the load
to be uniformly distributed on all the balls.

22. The retaining ring, or cage, and the balls of another
very simple form of ball thrust bear-
ing are shown in Fig. 14. The balls
run on the flat sides of circular, or
washer-shaped, races. In the best
form, no two balls are at the same
radial distance from the center of
the ring, so that each ball travels

over a separate path on each race. The race, therefore,
is not worn so rapidly as if all or several of the balls traveled
in the same path on the flat surface. It has been found that

Fio. 14

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BEARINGS AND LUBRICATION

§10

when the races are curved properly and all the balls run in
the same paths, as in Fig. 13, the bearings will generally
perform heavier duty than when made to operate on flat
thrust rings.

23. All the ball bearings that have been described are of
the two-point contact type. Other designs of ball bearings

s^j

Fig. 15

in which the balls have either one point of contact with
one race and two points of contact with the other race, or
two points of contact with each race, find some use, but not
such extensive use as those having two-point contacts.

24. Coiled-Roller and Ball Thrust Bear inprs.— The
application of colled-roUer bearings and ball thrust

bearings to automobile transmission gearing is shown

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BEARINGS AND LUBRICATION

in Fig. 15. The driving shaft a has two coiled -roller
bearings b and c and two ball thrust bearings d and e.
The power is transmitted through the bevel gears / and g
to gears in the case h, which are described elsewhere, and
through which the
power is transmitted
to the driving axles i
and /, they being en-
tirely separate and
independent. Each
axle has its coiled-rol-
ler bearing and ball
thrust bearing.

Fig. 16

25. Steerlngr-
Knuckle and
Wheel-Hub Bearings. — A steering knuckle and wheel
hub mounted on ball bearings are shown in Fig. 16.
The wheel bearings are of the cup-and-cone type. They

Fig. 17

can be adjusted by means of the nut a at the end of tht
horizontal spindle d that passes through the hub. By
means of a washer c, which has a projection fitting loosely
in a longitudinal slot in the spindle d, and a locknut 6,

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BEARINGS AND LUBRICATION

§10

the adjustment, when properly made, can be securely locked
without altering it. The thrust ball bearing is between the
steering knuckle and the upper fork of the axle. It carries
the downward pressure of the axle e against the knuckle /.

26. Fixed Type Bearinfir. — A driving, or traction,
road wheel mounted directly on the live axle is illustrated in
Fig. 17. The live axle c near the wheel is supported by a ball
bearing of the non-adjustable, grooved-ring, or annular, type.
The outer race a fits into the end of the stationary tube,
housing, or dead axle, /, as it is variously termed, which

Pig. 18

encloses the live axle. The inner race b fits on the live
axle c. The right-hand end of the live axle next to the
differential gear, which is not shown, is also supported on a
bearing. The hub of the wheel fits tightly on the live axle,
and is driven by the squared end d of the axle.

27. FloatinfiT-Axle Type Bearing:. — Fig. 18 illus-
trates a driving wheel mounted on the dead axle by two
ball bearings. This wheel is driven by a floating live axle
that does not carry any of the load on the wheel, but merely
serxes to drive the wheel. The inner races b and c are tightly
fitted to the tubular dead axle, and are rigidly held in place

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§ 10 BEARINGS AND LUBRICATION 17

by the nut e and the spacer / that lies between the races.
The outer race a is held by the ring nut ^ so as to have no end
motion in the hub, but the outer race d is left free to move
endwise, so as to adjust itself to the proper distance from the
outer race a. The race d fits closely in the hub, but not
tight enough to prevent the race from sliding when a moderate
end pressure is applied to it. The end thrust of the hub is
carried entirely by the bearing whose races are marked a
and h. The wheel is driven by means of a jaw clutch h that
fits over the squared end of the floating axle and engages with
jaws in the end of the wheel hub.

LUBRICATION

SYSTEMS OF liUBRICATION

28. liUbrication consists in introducing some sub-
stance, either liquid or solid, between two rubbing siuiaces,
to reduce the friction and the wear that otherwise would
occur. No matter how smooth a metallic surface may
appear to the sight or to the touch, it is in reality covered
with very minute projections or ridges and hollows. These
are readily seen under a microscope. Hence, when two clean
metallic surfaces are placed together and one is made to
slide or roll upon the other, these little ridges engage one
another, or interlock, with the result that some of the pro-
jections are torn loose from each piece. It is this tearing
away or abrading of the metal that causes wear, and the
resistance thus offered is known as friction.

When a lubricating substance, such as oil, grease, or
graphite, is put between the two surfaces, it fills the little
hollows and forms a thin film, or layer, that prevents the
metals from actually touching each other except at the
points of the highest ridges. As a result there is less wear,
since a smaller number of ridges are torn loose, and this
means less friction also.

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18 BEARINGS AND LUBRICATION § 10

Circulating systems of lubrication are described in con-
nection with the engines on which they are used. In other
lubricating systems, oil is fed more or less continuously to the
parts to be lubricated, but it is not returned to the lubricator
for use a second time.

29. Splash System. — In most engines, the crank-case
is completely closed, and a quantity of lubricating oil is
poured into the lower part of the case. At each revolution
of the crank the end of the connecting-rod dips into the oil,
splashing it about and thus lubricating the cylinder and
bearings of the engine. This method of lubrication is
termed the splash, system. In a number of engines, the
splash system of lubrication is relied on for the oiling of
the cylinders, but it has the disadvantage that the amount
of oil thrown depends largely on the speed of the engine,
and also on the degree of care exercised to keep a constant
oil level in the crank-case.

Several methods are employed to maintain the proper
level of oil in the crank-case. Sometimes a lubricator is
used to supply oil to the crank-case, and by trial it is adjusted
to feed the oil about as fast as the oil is consumed. In some
automobiles, this arrangement is not entirely satisfactory,
and it is necessary occasionally to pour oil directly into the
crank-case.

30. Some automobiles have the so-called forced-cir-
culation splash system. It consists of an oil well
located on the under side of the crank-case and a simple
plunger pump that is operated by an eccentric on the cam-
shaft. The oil well has a capacity of about 3 quarts. When
the system is in operation, the oil is raised from the well and
forced directly into the crank-case proper, filling its four
compartments. The oil finally overflows through a hole
provided for that purpose in the crank-case, and flows back
into the oil well. From the well the oil is again taken through
the pump, and in this way is kept in constant circulation.

31. Although the splash system of lubrication has been
found exceedingly satisfactory as regards the main shaft,

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§ 10 BEARINGS AND LUBRICATION 19

crankpins, etc., the sensitiveness of the cylinders to over-
lubrication or underiubrication has caused many makers and
users, especially of high-priced cars, to prefer separate
cylinder lubrication. In such cases, each cylinder is fed with
oil by an independent pipe from an oil reservoir, which is
located on the dashboard orN anywhere else near the engine.
Oil may be supplied by a hand pump to the crank-case
at intervals. Sometimes the main-shaft bearings are oiled
by individual oil wells, with oil rings or chains running
over the shaft and hanging down into the oil. These oil
wells are supplied with oil either at intervals by hand or
regularly from an automatic oiler. The rings or chains
rotate slowly and draw oil up to the rotating shaft. In this
case, the crankpins are commonly supplied with oil by some
centrifugal device, the oil being ptunped through a pipe and
caught by a centrifugal oil-catching ring attached to the
crank, and conveyed thence through holes to the crankpin.
Pockets may be cast over the crank-shaft and other bearings
so as to catch the oil that is splashed.

In automobiles having two or more cylinders mounted
vertically, one behind another, so-called baifle plates should be
provided in the crank-case to prevent all the oil from flowing
to the rear end of the crank-case in ascending steep hills,
or from flowing to the front end in descending steep hills.

Splash lubrication is used on vertical engines only, because
in horizontal engines it would be impossible to prevent an
excessive quantity of oil from being carried into the cylinder,
where it would cause smoke in the exhaust and would speed-
ily cover the spark plug with soot and clog the valves.

liUBRICATING DEVICES

32. Some of the devices for feeding oil to an engine
and other parts of an automobile are of elaborate construction ;
others are very simple. Lubricators that feed oil to the
rubbing surfaces of the bearings, the piston, and the cylinder
may be classified as gravity-feed, pressure- or compression-
feed, and pump-feed or mechanical lubricators.

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BEARINGS AND LUBRICATION

§10

GRATITT-FEED LUBRICATORS

33. SifiTlit-Feed Gravity Oil Cup. — A simple fonn
of slgrlit-feed graTity lubricator, called an oil cup,
is shown in Fig. 19. While it is rather unusual to attach a
lubricator directly to a horizontal cylinder of an automobile
engine as shown in this figure, the illustration is useftd as
an aid in explaining the principle of operation. The lubrica-
tor is placed at the top of the horizontal cylinder, and is

connected by oilways to the
rubbing surfaces of the cylin-
der and piston, as well as to
those of the piston pin and
connecting-rod. After the
glass cup has been filled, the
supply is regulated so that
about 5 or 10 drops of oil is
fed per minute. This is done
by turning the valve stem a
so as to vary the size of the
opening through which the
oil passes. The number of
drops that pass into the pis-
ton can be seen through the
sight glass d. Once adjusted,
the valve is locked by the
jam nut b. In order to turn
on or shut off the oil feed,
the arm c is turned to one
side, which can be done with-
out disturbing the adjustment of the quantity of oil supplied
to the piston. The sight glass d also permits the operator to
see whether the oiler is feeding properly. The oil passes
through the hole e to the piston /, and is distributed over the
surface by suitably cut oil grooves.

34. The piston pin is surrounded by the bronze bushing g,
and the wear is taken up by the screw h. Oil is supplied

Pio. 19

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§10

BEARINGS AND LUBRICATION

from the oiler to the piston pin through the tube i when it
registers with the hole e, or by hand when it registers with
the hole / in the cylinder wall. The oil tube k in the con-
necting-rod head receives oil from the tube i in the piston,
being directly below it. In order to be sure that the piston
pin is well oiled from the start, the crank-shaft is turned
until the piston has reached its outer dead center, when
the tube t will register with the oil hole / in the cylinder
wall and the oil tube k in the connecting-rod head. Oil
can then be supplied by a hand
oiler direct to the piston pin.
While the engine is running, some
of the oil supplied to the piston
finds its way through the tube t,
whence it is conveyed either di- ■
rectly to the tube fe or to a coun-
tersink in the connecting-rod head.
This countersink communicates
with the hole in the tube k through
small holes drilled horizontally
into the wall of the tube on a
level with the bottom of the coun-
tersink.

35. Cylinder Sifirht-Feed
Gravity Oil Cup. — Fig. 20 shows
a very good form of grravlty-f eed
cylinder lubricator. In case
of a strong back pressure from the cylinder, the brass
ball a will rise and close the opening; while, if the pressure
is not sufficient 'to lift the ball, the back pressure will
be taken care of by the tube 6, which extends above the
surface of the oil and permits the pressure to be equalized
above and below the oil in the lubricator. The lever c
when in a horizontal position closes the needle valve that
regulates the feed. The cup can easily be filled by sliding
the cover d to one side. When the lever c is in a vertical
position, the cup is feeding. The feed-tube extending well

Pig. 20

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22 BEARINGS AND LUBRICATION § 10

into the large sight-feed glass e prevents the oil from adhering
to or clouding the glass. The feed is regulated by the thumb
nut /, which is held in place by the spring g.

36. Multiple Siglit-Feed Gravity Ijubricator.

Fig. 21 shows a multiple oiler, with large glass ends a

through which the
amount of oil in • the
resen^oir can be seen.
The amount of oil going
to each bearing may be
noted at the sight-feed
glasses 6, and may be
regulated by the levers c,
^'<>- 21 on top of the reservoir.

Some arrangement for equalizing the pressure on top of
the oil, as in the single-feed lubricator just shown, is also
provided. Gravity-feed oiling devices are too uncertain in
their action and require too frequent adjustment and atten-
tion to be entirely satisfactory for automobile service.

COMPRESSION L.nBRICATORS

37. In pressure, or compression, lubricators, the

oil is forced out of the lubricator by either compressed
air or gas, which acts on the surface of the oil in the oil tank.
The pressure of the exhaust gases can be utilized for this
purpose in all types of combustion engines. In one- and
two-cylinder opposed engines, the intermittent compression
in the crank-case is also a source from which compressed air
can be obtained for .the compression tank of the lubricator.
In such engines, the air in the crank-case is compressed by
each out stroke of the piston or pistons.

38. A combined jcravity and pressure, or com-
pression, lubricator is shown in Fig. 22. In view (a)
a portion a of the front wall of the oil tank is shown; the
remainder of the front has been removed to show the interior.
The tank has four outlets 6, from which pipes lead to the parts

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§10

BEARINGS AND LUBRICATION

to be lubricated. Each outlet has a sight feed c and is
provided with a needle valve. A glass gauge d indicates
the height of oil in the tank. The plug, or cap, e is removable
for filling the tank. A pipe connected to / brings air or gas
under compression from the crank-case or exhaust pipe of

the motor into the space above the oil. In the following
part of the description it will be assumed that compressed
exhaust gases ^re used. The gas flows up / through a vertical
pipe y, past a check- valve k at the top of the pipe and tank,
and into the gas space of the tank over the oil. The wing

222—23

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24 BEARINGS AND LUBRICATION § 10

nut i is connected to a tube /, which has at its lower end a
bearing that is practically oil-tight; this tube also has an
opening m close to its lower end. When i is set, as shown,
for pressure feed, the oil is forced by the exhaust pressure
through the opening m, through the annular space between
the tubes / and n, and over the top of n, through which
it passes downwards into the horizontal passage o, which
communicates, through the needle valves p, with all the
sight-feed pipes q. After dropping through the sight feeds,
the oil passes through the check-valves r immediately below
them, so that it cannot be forced back by any accidental
pressure that may occur in the oil pipes from leakage of the
cylinder gases past the piston rings.

39. If it is desired to change the lubricator to gravity feed,
this may be done by giving the wing nut i a half turn, thus
bringing the opening m into communication with the opening s
— which at other times is closed — so that the oil will pass
directly from the reservoir into the passage o. The two
positions of the tube / are shown in the small sectional details
in Fig. 22 (6) and (c). The filling plug e, which screws down
air-tight, is provided with a vent check-valve connecting
with the stem /. By pushing down this stem, the check-valve
is opened and the compressed gas in the reservoir allowed
to escape, thus stopping the feeding of the oil, since it cannot
then rise to the top of n. This shotdd always be done, on
stopping the engine, to prevent flooding the cylinders or
crank-case with oil. The needle valves are opened for feeding
by turning the cam-pieces u to the vertical position shown.
When they are turned horizontally, the needle valves are
allowed to seat, thus stopping the flow of oil through the
tubes q. The needle valves are adjusted to the rate of feed
desired by screwing the caps v up or down, the opening being
increased by screwing them upwards. If an auxiliary oil
reservoir is provided, as is very often done, the oil is pumped
from it to the oil tank by hand through the connection g and
the plug valve h. The oil so forced is prevented from
returning by the check-valve iv immediately above h.

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§ 10 BEARINGS AND LUBRICATION 25

When no additional supply tank from which oil is pumped
into the sight-feed lubricator is used, the passage g can be
converted into an outlet by removing the check-valve w.
By connecting g to the crank-case of the motor, oil can be
fed into the latter in quantity by turning the petcock h to
the open position. This is a very convenient method of
putting oil in the crank-case after it has been drained and
cleaned. The method is also a good one to use when it
appears during a run that the pistons are not getting enough
oil and it is inconvenient to adjust the sight feeds.

MBCHANICAL. LUBRICATORS

40. In Fig. 23 is shown in cross-section an Indlvidnal-
pump lubricator, in which the oil is forced out into
each pipe by a force pump supplying that pipe only. The
grooved pulley a is driven by a belt from any convenient
rotating part of the engine, thereby causing the rotation of a
shaft having on it a worm 6, which, in turn, drives the worm-
wheel c mounted on the shaft d. Secured to this shaft d
are eccentrics e, whose number is one greater than the number
of pipes leading out to the parts to be lubricated. Each
eccentric, as it revolves, moves up and down in a yoke / that
is guided by the square stem g, which prevents the yoke
from turning. Each yoke is also connected below to the
pump plunger h. One of these plungers, not shown, has a
cross-section equal to all the others combined, and lifts oil
from the main reservoir i to the auxiliary reservoir, or oil
space, y. This oil space is separated from the chamber i by
a partition, and if more oil is supplied to the oil space than the
bearings take, it overflows into the chamber i. From the
reservoir ;, the oil flows down past adjustable needle valves k,
one for each outlet, to and through sight feeds /, and then
to each pump barrel through two ball check-valves w, the
first a very small one working horizontally and closed by a
spring, and the second working vertically and located directly
imder the plxmger h.

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BEARINGS AND LUBRICATION

On the down stroke of the plunger, the oil passes down
through a passage from m to n, and through the two small
check-valves n, each closed by a spring. The object of using
two check-valves instead of one, both before and after the

Fio. 23

pump is reached, is to maintain the action of the pump, even
if one valve happens to be put out of action by a particle of
foreign matter. In case this occurs, the other check-valve
will continue to act until the particle has been dislodged and
passed on with the oil.

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BEARINGS AND LUBRICATION

The oil feeds are adjusted by the needle valves k. The
oil passing through the sight feeds / is constantly under
suction, and the pumps are not able to draw a complete
chamberful of oil at any stroke. This prevents any accumu-
lation of oil in the sight feeds. The oil may be shut off
from any bearing at will, independently of the rest, by turning
the proper cam-lever o into the horizontal position, thus
closing the needle valve connected to it. Owing to the
great reduction of speed produced by the use of the worm b.
the action of the pump is very slow.

Pio. 24

41. Another force-feed lubricator with an individual
pump for each outlet, but no check-valves or stuffingboxes,
is shown in Fig. 24. Each plunger is operated by an eccentric
set obliquely on its shaft, so that the plunger is rotated
through an angle while near the top and bottom of its stroke.
The plungers are grooved in such a manner that they act as
their own valves. The lubricator is operated by a round belt
over the grooved pulley a, which turns a worm meshing with

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BEARINGS AND LUBRICATION

§ 10

the worm-wheel b on the shaft carrying the eccentrics. A
gauge glass c at the front of the case indicates the height of
the oil.

42. The pumps of this lubricator, which are immersed
in the oil, are of the same general construction as the one
shown in Fig. 25. The oil enters at a and passes out to the
oil pipe connected at b. The pump plunger has a vertical
groove c that is so located as to be in communication with a

when the plunger is ma-
king its up, or suction,
stroke, and is turned to
communicate with b
when the plunger is go-
ing down. The latter
position is the one
shown. By making the
plunger a true fit in the
pump barrel, and by
extending the barrel
considerably above the
intake and the outlet,
the leakage of oil is re-
duced to a minimtmi.
The stroke of the plun-
ger is adjusted by ma-
king the eccentric in
two parts, d and e,
which are really two ec-
centrics, the eccentric d
being held on the shaft by a setscrew /, and the eccentric e being
held from rotating on d by setscrew g. These eccentrics may
be turned relatively to each other to give them an effective
net throw of anything from zero to the combined throw
of both.

The simplicity secured by the elimination of valves and
springs, as well as stuffingboxes, is a desirable feature of
this lubricator.

Pig. 26

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§10

BEARINGS AND LUBRICATION

43. Precision Oiler. — Another mechanical oiler,
known as a precision oiler, that can be made to feed as
many bearings as desired is shown in section in Fig. 26.
It has no valves, check-valves, or stufiingboxes. Its prin-
ciple of operation is as follows: The vertical shaft a is driven
from the engine by a mechanism, not shown, on top of

Pig. 26

the case. There are as many of these shafts as there are
separate bearings to feed. The worm on the base of this
shaft rotates the wheel b in the direction of the arrow. On b
are two cams: one cam c works in the rocking fork d; the
other cam e raises the lever / and lets it return under the
pressure of the spring g. The fork d is supported on trun-
nions at h, and moves with the pump barrel i, whose base

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30 BEARINGS AND LUBRICATION § 10

forms the segment of a cylinder, as shown. The plxmger ;
has a slotted head, in which the lever / works with some lost
motion. In the position shown, the cam e is about to lift /,
• raising the plimger ; with it, while the cam c is imparting no
motion to d\ thus ; draws oil into i through the intake k.
Presently, while the cam e still holds /, the cam c rocks d
and i until the plunger is opposite the delivery port n. Then e
releases /, while c holds d stationary, and the downward
stroke of /, produced by spring g, discharges the oil into «.
The use of a spring instead of a cam to force down the pump
plunger avoids breakage, in case the delivery pipe is choked.
The stiffness of the spring, however, is sufficient to overcome
any ordinary obstruction. Then d and i are rocked back to
the intake position, and the process is repeated.

The end bearing of the trunnion, instead of being fixed, is
carried in the piece /, which can be adjusted to take up wear
in the base of i and its seat. Provision, is made for regula-
ting the stroke of / by turning the stem m, which screws up
or down in a nut at the bottom, so that the left end of / is
raised or lowered, permitting a variation of motion of / in
the head of / on the lift of the cam. It will be noticed that /
cannot come in contact with the valve seat, the lower end of
the barrel i being tapered to act as a stop.

COMPARISON OF LUBRICATORS

44. One advantage of the mechanically operated lubri-
cator over those which depend on either compression or gravity
for the flow of oil from them is that the mechanical lubricator
always delivers the same quantity of oil per stroke of the
pump or any other mechanical device that forces out the oil.
Since the pump is driven at a speed proportional to that of
the rotation of the engine, the amount of oil delivered to the
engine is proportional, or at least approximately proportional,
to the speed of the engine. This is desirable because the
engine, especially the piston and cylinder, requires more oil
per minute when running fast than when running slow.

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§ 10 BEARINGS AND LUBRICATION 31

The gravity lubricator, on the other hand, delivers a
lubricant at a constant rate just as long as the oil continues
to be of the same thickness, or viscosity. The engine therefore
gets as much oil when running slowly as it does when running
rapidly. The same is at least approximately true of pressure-
feed lubricators. If the oil thickens, as during the cool part
of a day, the gravity and pressure lubricators deliver it at
a slower rate. The flow can, of course, be regulated by
adjusting the needle valves at the feeds, but this is rather
undesirable. Sometimes, on cool mornings, oil that is
ordinarily thin enough to flow freely through a nearly closed
valve, will not flow at all from a gravity lubricator, even
when the feeds are fully open.

A lubricator can, of course, be placed on or near the engine,
so that the oil will be kept warm enough by the heat from
the engine to flow freely after the latter has become warm
from running, but the sight feed of a gravity lubricator
cannot be seen when it is in this position. The
mechanically operated lubricator can be piped
up to sight feeds on the dash, where they are
visible to the driver. This method has been
adopted to a considerable extent. The gravity-
feed lubricator, when used in connection with
an engine imder a hood at the front part of
the car, can be kept warm to some extent by
placing it on the front side of the dash next Fig. 27
the engine. When so placed, the sight feeds can be carried
through the dash so as to be visible to the driver.

OIL. AND GREASE CUPS

45. on Cups. — A very simple oil cup used on steer-
ing knuckles and other movable joints that require only a
little oil occasionally is shown in Fig. 27. It is generally
screwed into the top of a hollow spindle, from which holes
lead to the bearing surfaces. By turning the nurled piece a,
the hole b in the cover can be placed opposite a hole in the
body of the cup; then oil can be introduced into the center

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BEARINGS AND LUBRICATION

§ 10

hollow part by means of an ordinary oil can. The oil will
run down to the hole in the spindle and the hole or holes
leading from the central one to the bearing surfaces. After
introducing the oil, the nuried nut should be turning so as to
keep dirt and dust out of the interior. Small oil cups for
such purposes are made in various other ways.

46. Grease Cups. — The bearing surfaces for wheels,
drive shafts, universal joints, steering gears, and knuckles
are often lubricated with grease fed through grease cups.
A very simple grease cup extensively used on automobiles
is shown in Fig. 28. The cap a is unscrewed from the body fe,
nearly filled with a suitable grease, and screwed on again to

Pig. 28

Fig. 29

Pig. 30

about the position shown in the figure. The body b is
permanently screwed into a hole that runs to the bearing
surfaces. The pressure of the cap a upon the grease, together
with the heat developed at the bearing surface, is sufficient
to feed the grease to the bearing. The cap should be given
a 'turn or two each time the automobile has run a certain
distance. When the cap is screwed down as far as it will
go, it should be removed, refilled, and replaced.

47. A better grease cup, but one not often used on auto-
mobiles is shown in Fig. 29. It has at 6 a packing of leather
or other suitable material that is held in position by the
threaded piece a, which should be tight enough to make the

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§ 10 BEARINGS AND LUBRICATION 33

packing fit close to the cap thread. Dust is less liable to
enter this cup than the one shown in Fig. 28; also, its cap is
less liable to jar loose.

48. In Fig. 30 is shown a ratchet gri*ease cup used
on automobiles. It is provided with a bottom piece a that
cannot rotate, but can move up and down. The spring b
presses the piece a up against the lower edge of the cap d,
and when the projection c corresponds with the notch in the
lower edge of the cap, the latter is usually held so tight that
it will not be unscrewed by vibration; nevertheless, it can
be readily turned by hand. This grease cup is suitable for
use on moving or jarring parts of an automobile, as the
construction tends to prevent the unscrewing and loss of
the cap.

Grease cups are made of polished, nickel-plated, or rough
brass, or of steel. The threads on the shanks are usually
standard iron-pipe threads, varying in size from J to J inch.
Grease cups vary in capacity from J ounce to 6 ounces of
grease, the cups of smaller size having the smaller-sized
shanks.

49. Automatic i^ease . cups have a leather-washer
piston that is pressed downwards by a spring between it and
cover of the cup. Thus, the grease below the piston is
constantly pressed toward the bearing by the piston and
spring. The piston is attached to a threaded rod that
projects through the cover and has on it a thumb nut that
can be turned for compressing the spring, so as to raise the
piston when the cup needs filling. The shank also is usually
provided with a screw, by means of which the size of the
opening through which the grease is fed to the bearing may
be varied. By this means the rate at which th§ grease is
fed to the bearing may also be varied.

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34 BEARINGS AND LUBRICATION § 10

AUTOMOBLLE OlliS

PROPERTIES OF OIL.8

50. There are four properties that a good automobile-
engine cylinder oil should possess.

1. It should have as high a fire test as possible; that is, the
temperature at which it gives off inflammable vapor should
be as high as possible. In the best automobile-engine cylinder
oils, this temperature will be from 600° to 650° F., which is
none too great considering the temperatures to which the oil
is subjected when exposed to the burning charge in the
cylinder.

2. As the oil is vaporized by the heat, it should leave as
little residue as possible. Any cylinder oil will leave some
carbon deposit, which gradually accumtilates on the inner
walls of the combustion chamber and on the piston head and
valves, but it is desirable that this accumulation should be
prevented so far as practicable. If it becomes thick, espe-
cially if the compression is high or if the form of the com-
bustion chamber is such that sharp comers are exposed
to the heat of the flame, particles of the tmburned carbon
clinging to the walls or elsewhere may become heated to
such a degree as to ignite the charge spontaneously before
compression is complete.

3. The oil must also have good lubricating qualities,
which may generally be taken to mean that it has sufficient
viscosity; in other words, that it is not excessively thin.
On the other hand, however, the cylinder oil should not be
very thick, else it will not satisfactorily lubricate the bearings
of the crank-shaft and connecting-rod.

4. There should be no acid in any oil or grease used for
lubricating any part on automobiles. The presence of any
acid is dangerous to the metal parts, since it attacks and
corrodes them. The corroding action of an acid is especially
objectionable when ball bearings are used. The surfaces of
the balls and the races on which they are run must be exceed-

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§ 10 BEARINGS AND LUBRICATION 35

ingly smooth in order to give good service. If these surfaces
are injured by corrosion, the life of the ball bearings will
be greatly shortened.

5 1 • Grades of Oils . — For ordinary water-cooled engines,
except in the largest sizes, the grade of cylinder oil kno^^ n
as heavy is appropriate for summer use. In weather cold
enough to cause this oil to stiffen, the next lighter grade,
or medium, may be employed. In cold weather, if the
medium oil does not feed freely, it is best to use a speLial
oil that will not become too thick at low temperatures,
although the regular oil can be thinned just enough w ith
kerosene or gasoline to make it flow properly and to inc rease
correspondingly the feed of the oil cup or mechanical luKiri-
cator. For air-cooled cylinders, only the heaviest oil olitain-
able and with the highest possible fire test should be used,
and the oil tank should be placed near enough to the cylinder
or exhaust pipe to insure that the oil will not refuse to feed
in cold weather. It is best in every case to purchase oil that
is known to be reliable.

If the oil is light or thin, more of it must be used than of a
heavy oil to accomplish the same result, since the light oil is
more easily decomposed by the heat in the cylinder than h the
heavy oil. The object is to feed enough oil to insure |>er-
feet freedom of running and little wear of the piston .md
rings. At the same time, it is well to avoid the use of more
oil than is necessary, as this will result in the formation of
carbon deposits from the burned oil, and a consequent
tendency to preignition, clogging of the valves, sooting of
the spark plugs, etc. In any case, only a high grade of min-
eral cylinder oil should be used, as the troubles that folbjw
the use of an inferior oil will more than offset the sli^^ht
saving in cost.

Some manufacturers of automobiles sell oils marked with
their own labels that they recommend for use in their engines.
These oils may generally be used with confidence in any
engine of about the same character as that for which thev are
put up.

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36 BEARINGS AND LUBRICATION § 10

52. TestinfiT of Oils. — Oils may be tested for viscosity
by putting a few drops of each kind on an inclined sheet of
clean metal or glass, or an old, but clean, china plate or
saucer, and noting the relative rapidity of their downward
flow. The oil that flows most rapidly has the least viscosity,
and the one that flows most slowly has the greatest viscosity.

The oils may be tested roughly for flashing point and for
the carbon residue they leave by putting a little on a sheet of
iron or tin plate, or on an old china plate or saucer, and heating
gradually over a flame, taking care to move the plate o\er
the flame so that all parts of it are evenly heated. The
oils will become less viscous and will run on the plate, and for
this reason two samples compared at the same time should
not be placed too close together. They will gradually
vaporize, leaving only a brownish and somewhat thick
residue, which should be as small in amount as possible. A
good, heavy oil will vaporize almost completely, but will
retain considerable body even at temperatures where an oil
of low fire test wotdd be entirely burned away. Oils, either
heavy or light, that leave a considerable amount of black,
gummy residue should be avoided. It is, of course, difiicult
to tell at just how high a temperature the vaporization occurs
in this test. If, however, an oil that is kno^vn to be suitable
is at hand, a new oil can be compared with it by putting a
few drops of each on the plate and heating the latter uniformly
where the two oils are placed.

The test for acid in a lubricating oil can be made by satu-
rating a piece of cord or thread with some of the oil, and then
wrapping the thread around or laying it on a polished piece
of iron or steel, after which the whole can be exposed to the
sun. If acid is present in the oil, the bright surface of the
metal will be corroded in the course of a few hours along
the side of the string.

53. Cylinder Oil. — ^Althotigh, strictly speaking, cylin-
der oil needs to be used only for cylinder lubrication, it is
the almost universal custom to use the same oil for all bearings
of the engine. This simplifies the lubrication and removes

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§ 10 BEARINGS AND LUBRICATION 37

the danger of making a mistake in oiling the pistons. Cylin-
der oil is an excellent lubricant for bearings subjected to hard
service, as those of the crankpins and crank-shaft. The
bearings do not require so much oil as the pistons, 4 or 5 drops
a minute usually being sufficient.

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AUTOMOBILE TIRES

TIRE CONSTRUCTION AND APPLICATION

TTPE8 OF TIRES
I^TRODUCTION

1. The tires used on automobiles may be divided into
three general classes, namely, pneumatic, cushion, and solid
tires.

2. Pneumatic tires are divided into two subclasses:
single-tube and double-tube tires,

Slniarle-tube tires resemble an endless ring of ordinary
rubber hose, the inside being filled with air under pressure.
While widely used on automobile wheels in the early days
of the automobile industry, their inherent defects have caused
a gradual passing away, until at present single-tube tires are
seldom used. on automobile wheels.

Double-tube tires consist of two parts, namely, an outer
part composed of rubber and fabric, and called a casing, or
shoe, and an inner part in the form of a hollow cylindrical
ring made of soft rubber, and called an air tube, or inner tube,
or, for short, a ttibe. Pneumatic tires are today in almost
universal use on pleasure automobiles, where ease of riding
is of prime importance.

3. Cusblon tires are made of fairly soft rubber in a
variety of shapes intended to give a cushioning effect. They
are used to a limited extent.

COPTMIQHTCO BY INTCMNATIONAL TEXTBOOK COMPANY. CNTCRCD AT •TATIONCRB* HALL. LONDON

222—24

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AUTOMOBILE TIRES

§11

4. Solid tires are made of rubber or of wooden blocks,
and, as implied by the name, they are solid in structure,
although slightly resilient. They are used mostly on heavy,
slow-speed automobiles, such as those used in the commercial
field, although occasionally they are fitted to light-weight
delivery cars and to some forms of pleasure cars.

5. The various tires, tools, tire appliances, etc. here
shown and described have been selected from those on the
market as most clearly exhibiting the salient features of the
types that they represenjt. The fact that certain automobile
accessories are here shown and described must not be con-
strued to mean that they are superior to all other devices
designed for similar service.

PNEUMATIC TIRES

6. Types of Pneumatic Tires. — A cross-section of a
single-tube pneumatic tire in place on the wheel rim is illus-
trated in Fig. 1. The tire a is made up of several layers,

or plies, of cotton or
linen fabric of very
open weave embedded
in the rubber. The
latter forms the air-
tight, waterproof por-
tion, and, externally,
the wearing surface of
the tire. The fabric is
shown in four concen-
tric dotted circles in the
figure. For mechanic-
ally fastening the tire
to the wheel rim fe, a
number of tire lugs c
are provided. These
lugs project through the wheel rim and are tapped to receive
a lug screw d, which holds in place a clamp e that bears against
the wheel rim and holds the tire in place.

Fig. 1

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§ 11 AUTOMOBILE TIRES 3

Instead of using the method of fastening just described,
some makers of single-tube tires use studs that are per-
manently fastened to the lugs; these are then wholly inside
the tire, and the tire is fastened to the rim by means of clamps
and nuts attached to the studs. Single-tube tires thus
attached are intended for use on wire wheels, and cannot be
readily used on artillery wheels. Single-tube tires made to be
attached as shown in Fig. 1 can be applied to either wire
wheels or artillery wheels, provided screws of sufficient length
are used.

7. Single-tube tires are made with either five or eight tire
lugs; hence, in ordering them, care must be taken to specify
the number of lugs required by the wheel rims^. The correct
length of lug screw, as well as whether the tire is wanted for
a wire wheel or an artillery wheel, should also be stated.

Although the single-tube tire is simple in its construction,
at present it is seldom applied to automobiles for the reason
that it is extremely difficult to repair in case of a puncture
or other air leakage due to general deterioration produced
by the regular wear of the tire in rolUng over the roadway
and coming into contact with stones and other uneven
parts of the road.

8. Double-tube pneumatic tires may be divided into three
types, namely, clincher, mechanically fastened, and quick-
detachable tires.

Clincher tires are tires that are fastened to the rim
chiefly by the pressure of the contained air, usually aided by
a few special clamps.

Mechanically fastened tires are tires that are held to
the rim by mechanical means.

Quick-detachable tires are tires that are made either
with the same outline as a regular clincher tire or with a flat
base, the quick-detachable feature being secured by a special
construction of the rim.

9. In Fig. 2 is shown a short section of a double-tube
pneumatic tire of the regular clincher type in place on the wheel

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AUTOMOBILE TIRES

§11

rim. The casing, or shoe, a of the tire, instead of being com-
pletely tubular, is open along the side next to the rim b. The
middle of the rim is nearly flat and the edges are curved
inwards toward each other, as at c, so as to form a clinch on each
side for holding the tire casing in place. The casing is formed
with beads d that fit into the clinches of the rim. An inner
tube e of soft elastic rubber, without any interwoven fabric,
is placed inside the casing. This inner tube retains the air
in the tire. It is provided with a valve through which air

can be forced into the tube
by means of a pump or some
other device, and the valve
can be opened to allow the
escape of air from the tube
when it is to be deflated.
This air valve is not shown
in Fig. 2. The pressure
of the compressed air forces
the beads of the casing into
the clinches of the rim and
retains them there so that
the tire is held in place when
fully inflated. In order to
secure the tire more firmly
to the rim, that is, so that
it will not be thrown out
when a side pressure is
exerted upon it, as when a car is turning a curve at high
speed, devices variously called tire lugs, clamps, clips, or
security bolts, of which the head of one is partly shown at /,
are provided. The head / of the tire lug is shaped to conform
to that part of the casing with which it is in contact. A bolt
extends from the head of the lug inwards toward the center
of the wheel, and is threaded to receive a nut g, which is used
to draw the head of the clamp down tight against the inside
of the casing.

The thickest portion of the tire is shown at h, and is called
the tread of the tire. It is the part that comes into contact

Fig. 2

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§11

AUTOMOBILE TIRES

with the roadway when the tire is in regular use. One or
two strips of fabric, called breaker strips^ are generally placed
between the tread and the main portion of the fabric. These
strips strengthen the casing, and in case of great wear become
exposed and thus indicate the necessity of repair.

When an ordinary clincher tire of the form just described
is being placed upon the wheel rim or removed from it, the
beads of the tire must be lifted over the clincher portion of the
rim. The outside diameter of the clinch is larger, of course,
than the inside diameter of the bead of the casing. The bead
must therefore be elastic enough to stretch sufficiently to pass

Fig. 3 Fio. 4

over the clinch. In the tire shown in Fig. 2, each bead has a
rubber filling that is elastic enough to allow the tire to expand
as just described.

10. The Flsk bolted-on tire, a short section of which
is shown in Fig. 3, is an example of a mechanically fastened
double-tube pneumatic tire. The rim a of the wheel is made
of a flat strip of steel. The part of the tire casing in contact
with the rim is also made flat. Two retaining rings b held in
place by means of bolts that extend from side to side through
the tire just outside the wheel rim, are provided to hold the
tire in place. The head of one of the bolts is shown at c, and

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G AUTOMOBILE TIRES J 11

the nut on it at d. The head fits over the side of the wheel
rim a and retaining ring 6, and a clamp e just under the nut d
fits the wheel rim and ring on the opposite side. The tire
casing is split circumferentially at / in a plane perpendicular
to the axis of the wheel.

11. One of the first quick-detachable tires to be placed
on the market, and one that is now made by many tire
makers, is the Dunlop tire. This type of tire is also known
as the -flat-base type quick-detachable tire, A short piece of
such a tire, moimted on what is called the standard universal
quick-detachable rim, is shown in Fig. 4. This tire has no
means of clinching it to the rim as has the regular clincher

tire previously described.
Therefore, to prevent the
inner edges of the Dunlop
casing from expanding ap-
preciably in diameter when
the tire is inflated, endless
wires, shown projecting
from one edge of the casing
at a, are employed. These
wires form a ring that is,
of course, inexpansible in
comparison with fabric
such as is ordinarily used in tires, and hence a tire of this
kind cannot be put in place or removed over a clinch. For
this reason, one or more removable rings that form part
of the wheel rim are provided to hold the casing in place
and permit of its ready removal from the rim. Thus, in the
the figure, the solid retaining ring b can be removed from the
wheel rim c by pressing the ring in toward the center of
the rim after the tire has been deflated, and then removing
the split ring d from the groove of the wheel rim into which
it fits. After removing the rings b and d, the complete tire
can be slipped off sidewise from the wheel rim. No tire lugs,
or clamps, are required for a tire that has metal (wire) rings
embedded in its edges.

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§ 11 AUTOMOBILE .TIRES 7

A loose protective flap e in the shape of a channel ring is
furnished by some tire makers. This flap is placed between
the edges of the casing to form a close joint and a smooth sur-
face for the inner tube to bear against. The flap is generally
made of rubber strengthened by embedded woven fabric.

12. Fig. 5 shows a modified form of clincher tire, in place
on the type of rim shown in Fig. 4. This form of tire is called
a quick-detacliable clincliep tire. This tire is pro-
vided with endless wire bands a of the same fqrm as those
used in the Dunlop tire shown in Fig. 4. Referring again to
Fig. 5, it will be observed that the right-hand side of the rim
is bent up to form a clinch. For the Dunlop tire, the groove
under the clinch is filled with a ring /, Fig. 4, of hard rubber,
so as to form a surface that conforms to the outer side of the
edge of the casing. With the tire shown in Fig. 5, no hard
rubber filling is used, and, besides, the solid retaining ring h
is turned around so that its grooved clincher side is brought
next to the casing. When made up in this manner, the rim
resembles closely the ordinary one-piece clincher rim so far
as the form of the space into which the beads of the tire casing
fit is concerned. The endless wire bands give the tire greater
rigidity and a stronger grip on the wheel than is secured when
the elastic material of the casing, together with the tire lugs,
is depended on to hold the casing in place. A tire of this form
cannot be removed or applied by stretching it over the edge of
the clinch. Both the solid ring h and the spUt ring c must be
removed in order to take off the casing or to put it on the rim.

13. In connection with quick-detachable clincher tires,
it is to be noted that such a tire cannot be applied to a regular
clincher rim^ A regular clincher tire can be applied to a rim
designed for a quick-detachable clincher tire of the same size,
but it is not advisable to do this because quick-detachable
clincher rims are usually not drilled for tire lugs, or security
bolts.

14. Removable, or Detachable, Kims. — The object
of using a detacbable rim, that is, a rim that can be

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AUTOMOBILE TIRES

§11

removed from the wheel, is to secure a ready means for
changing tires, as, for example, when the one in use has
become defective. By having the rim detachable, a com-
plete spare tire can be carried inflated on an extra rim, so that
the arduous work of changing the tire on the rim and inflating
it is eliminated. If the detachable rim and its fastenings
are of proper form and in good condition, they can be quickly
removed ; a spare tire with its rim can then be substituted in
much less time than is ordinarily required for putting on a

tire, together with its inner
tube, and then inflating it.
Numerous forms of
quick-detachable mount-
ings for tires are used, each
with its own distinctive
method of removal and re-
placement. Whether or
not they may be considered
desirable depends on the*
readiness and ease with
which they can be changed,
and the absence of lia-
bility to become, by rust-
ing, or otherwise, boimd in
place so as to make it
very difficult to remove
them, or even to make it
Fio. 6 necessary to break some

of the parts in order to get them off.

15. Fig. 6 shows a removable wheel rim applied to a tire
of the same form as that illustrated in Fig. 3. Between the
rim a and the wooden felloe, or felly, fe, as it is sometimes
called, is placed a second rim c and a split expansion locking
ring d. This ring is held in place by bolts, of which one
marked e is shown in place. The rim a is fastened by tight-
ening the nut / so as to force the expanding ring d against the
inclined surface of the inner rim c. When the nut has been

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§11

AUTOMOBILE TIRES

tightened completely, the flange g on the expanding ring bears
against one side of the channeled portion of the outer rim
and forces it against a flange h on the opposite side of the
channeled portion, thus locking the outer rim a rigidly in
place.

In order to facilitate the removal of the tire from the
detachable rim a, an angular air valve is used. The head
of the valve stem is shown at i inside the inner tube, and the
cap y of the valve stem at

one side of the tire, be- n^^j I '>^ -ft

tween the rim a and one
of the retaining rings.
The connection for infla-
ting the tire is made at ;.

16. Spare Wheels.

Instead of making only
the tire and its rim detach-
able, as described in Arts.
14 and 15, in one method
the wheel rim, spokes, and
part of the hub, together
with the tire, are made
removable. This combi-
nation is known as a spare
wheel. When in place
for use, the spare wheel is
fastened to the part of the
hub that always remains
on the axle or front spindle
by means of bolts that pass through the hub flanges and are
easily removed under ordinary conditions.

In another method, a fully inflated tire is carried on a spare
rim provided with clamps, by means of which it can be quickly
attached to the felloe of a wheel carrying an injured tire,
which is left in place until time is found to repair or replace it.

17. Tire Air Valves. — In the United Stages, the kind
of check- valve in practically universal use for admitting

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10 AUTOMOBILE TIRES § 11

air under pressure to a single-tube tire or inner tube and
retaining it therein, is that known commercially as the
Sclirader valve. The one made for inner tubes is illustrated
partly in section in Fig. 7 (a). In Fig. 7 (b) the air check,
which is known commercially as the valve insides, is shown
to an enlarged scale.

Referring to Fig. 7 (a), the stem head a is inside the inner
tube, and a metal washer b is clamped down against the tube
by means of the nut c, which fits on the threaded body of the
large hollow stem d. The inner rubber tube is reinforced
with an additional thickness of rubber that is cemented on
at the point where the valve stem is attached to the tube.
Between b and c is a guard, or spreader, e that prevents the
inner tube from coming into contact with the nut c. This
guard also fits against the side of the shoe, so as to make a
tight joint for the bearing surface of the inflated inner tube.
The large hollow stem is flattened on two opposite sides
(one of the fiats being shown at /) so that it can be held with
a wrench or in some other manner to prevent it from twisting
around while tightening the nuts. The nut g, when tightened,
presses the washer h, which may be of either leather or rubber,
against the felloe. The stem d is pierced from end to end
with a hole i. The end / of this hole is threaded to receive
the air valve and the parts attached to it, as shown in
Fig. 7 (6).

The outside of the valve stem is reduced in diameter and
threaded to receive a small cap k for closing the outer end of
the hole through the tube. This cap thus protects the valve
from dust and other foreign matter, and at the same time
provides an air-tight joint that prevents loss of air from the
inner tube, in case the air check-valve should leak. Leakage
of air is prevented by the rubber packing disk, or washer, /,
which bears against the end of the valve stem when the cap
is screwed in place. A large dust cap m screws over the
larger portion of the stem against a leather washer n, and
thus forms a protection for the entire end of the stem, which
would otherwise be exposed.

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§ 11 AUTOMOBILE TIRES 11

18. As shown in the enlarged view, Fig. 7 (fe), the valve is
provided with a short threaded piece o that screws into the
end of the valve stem. When this piece is screwed down to
the proper position, as shown in Fig. 7 (a), the conical rubber
packing ring /?, view (6), presses against a corresponding coned
surface in the hole through the stem, and at the same time
a thin brass cup-shaped piece q bears against a square shoulder
farther down in the hole through the valve stem, so as to com-
press the coiled expansion spring r, and thus force the valve s
up toward the valve seat /. The valve s is provided with a
soft-rubber valve disk «, against which the comparatively
sharp edge of the valve seat / bears when the valve is closed.
The packing ring p when pressed down against the coned
internal surface of the bore of the valve stem makes an air-
tight joint. When air is passing through the valve into the
inner tube of the tire, the valve 5, together with its rubber
disk «, is forced away from the valve seat i by the pressure
of the air against the valve disk.

When it is desired to allow the air to escape, the valve can
be opened against the pressure of the air in the inflated tube
by pressing against the end of the solid stem v. The only
part rigidly attached to this stem is the valve 5, so that when
the stem v is pushed in against the coiled spring r, the valve 5
is forced away from the valve seat i. As soon as the valve
and seat are separated, the air can escape.

19, In order to provide a ready means of screwing the
' valve into place and removing it, the small cap k has a slot w

across an extension of its outer end and the end of the part o
is cut away so as to leave projections x, over which the slot w
fits. The two parts together thus operate as a screwdriver
and a slotted screw head. The stem-Uke extension of the
cap k, across which the slot w is cut, fits loosely into the end
of the valve stem, and can therefore be readily inserted to
screw the valve into place. The rubber packing / in the
small cap has a depression on the side next to the valve, in
order to prevent it from striking the end of the small stem v
in case the latter happens to project beyond the end of the

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§11

main valve stem d. The rubber packing is correspondingly
crowned on the side opposite the depression so as to secure
sufficient thickness of material. The small solid valve stem
is flattened at both ends so that the parts of the valve will
not fall apart when removed from the main valve stem.

20. Another valve stem with its valve in place is shown in
Fig. 8. .This type, known as the Scovill valve, has been
used on bicycle tires and on many automobile single-tube
tires, but is now rarely used. It is described chiefly because
of the fact that its valve insides and the insides of the more
commonly used Schrader valve are interchange-
able so far as screwing them into the hollow
valve stem is concerned, but neither will make
an air-tight fit in the stem that is suitable for
the other.

As shown in Fig. 8, the large hollow valve
stem is threaded inside at one end to receive a
threaded plug b. When this plug is screwed
into place, it presses the valve seat c against
the shoulder d in the bore of the hollow stem and
also squeezes the rubber packing ring e, so that
this ring is pressed against the surrounding parts
and forms an air-tight joint. A small solid valve
stem / passes loosely through the plug b and the
valve seat c, and has rigidly attached to its
inner end a valve g provided with a rubber
disk A, which forms a seat for the valve. The valve is
held against the valve seat by a coiled expansion spring t,
one end of which bears against the valve g and the
other end against the shoulder at the end of the larger
portion of the bore in the hollow valve stem a. The entire
valve mechanism is connected to the tire by means of a
rubber tube that slips over the hollow stem a, and the
air passes first through the hollow stem and then out of the
opening / into the tire during the process of inflation. While
air is passing into the tire through the valve stem, the valve g
is forced away from the valve seat c. In order to deflate the

Pio. 8

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AUTOMOBILE TIRES

tire, the small solid valve stem / is pressed inwards by hand
to force the valve g away from the valve seat 6.

21. On account of the difference in form of the two
valves just described and of the shoulders against which they
press to form an air-tight joint, as well as the different methods
of applying the expansion spring, neither valve will operate

Pio. 9

successfully in the valve stem intended for the other, as has
already been stated.

Tire air valves differing in form from those described have
had and still have a limited use.

Schrader valves are made with different lengths of stems
to suit different sizes of inner tubes and thicknesses of wheel
felloes; hence, when ordering inner tubes, it is well to specify
the length of valve stem required.

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14 AUTOMOBILE TIRES § 11

22, Tire Lui^. — Several forms of devices for fastening
an ordinary, or plain, clincher tire on the wheel rim are
illustrated in Fig. 9. The lug shown in view (a) has a rubber-
covered head, or spreader, a, inside of which is a piece of
metal formed to a suitable shape, and to which is attached
the threaded stem b. The nut c is made cap-shaped to
protect the stem. A leather washer is usually placed between
the nut and the felloe of the wheel, in order both to make a
tight joint and to reduce the liability of the nut to work loose.

In view (6), the head a, which fits inside the shoe between
it and the inner tube, is made of canvas on the side that comes
against the shoe and of leather on the other side. The metal
portion of the head lies between the leather and the canvas.
The stem b has the same form as the stem of the lug just
described and passes completely through the nut c. A lock-
nut d is also placed on the stem, and it is screwed down against
nut c in order to lock this nut in place after it has been suffi-
ciently tightened. The locknut d is cap-shaped and is closed
at the end to protect the stem.

In order to eliminate the necessity of using a wrench for
tightening the tire lugs, a wing nut, or thumb nut, e, as shown
in view (c), is sometimes used on lug stems.

In view (d) is shown a split nut over which slips a ring, or
sleeve, / with wings resembling those used on an ordinary
wing nut. The purpose of this device is to secure a quick
means of moving the nut along the stem. The nut is so con-
structed that when the sleeve / is sHpped up from the threaded
and split lower end g of the nut, as shown in the illustration,
the threaded parts of the nut separate from each other on
accotmt of their elasticity and thus disengage from the thread
on the stem. The nut can be slipped along the stem when
opened out in this manner. Then, by slipping the sleeve /
down to the threaded end of the nut, the threads are brought
into engagement with those on the stem and the nut can be
screwed along the stem in the same manner as in an ordinary
nut. It is doubtful whether the time that can be saved by
using such a nut on tire lugs is enough to warrant the sub-
stitution of a split nut for one of the ordinary kind.

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§ 11 AUTOMOBILE TIRES 15

23, The head of a tire lug, clip, or clamp must be of such
form as to fit closely and smoothly against the inside of the
tire casing. It should also fit against the wheel rim in the
same manner when the latter is not completely covered by
the casing; otherwise, a hole will be blown through the inner
tube or the tubes will be locally stretched and permanently
distorted around the head of the lug. The excessive local
stretching will weaken the rubber and ultimately will likely
cause a hole, which may not occur, however, tmtil the tube
has been removed, put in a casing, and inflated again.

Tire lugs are made of different forms and sizes to suit the
make and size of tire on which they are intended to be used.
In general, a lug intended for the tires of one manufacturer
will not fit those of another; neither will a lug for a small tire
fit a large tire of the same make, or vice versa.

Tire clamps, or lugs, are sometimes omitted on clincher
tires, in which case the friction of the bead in the rim is
depended on t6 keep the tire from creeping around the rim.
The tires seem to be very effectively held in this manner as
long as they are fully inflated. However, if the tire on a
rear wheel (traction wheel) is run after it has become partly
deflated, it is liable to creep around on the rim. When this
creeping occurs,, there is danger of shearing or of tearing the
valve from the inner tube.

If tire clamps are not used on a rim that has holes for them,
the holes should be tightly plugged. The plugs used for this
purpose must be smoothed down flush with the rim where the
tire bears against it.

Tire clamps serve to prevent the shoe from being pulled
from the rim when turning curves, and also to prevent it from
creeping around on the rim. The results of leaving clamps
off seem to indicate that they are not actually necessary
except when the tire becomes deflated. Although a car
should not be nm on a deflated tire, it is frequently done
before the fact that the tire is deflated becomes known.

24, Inner Tubes. — Although each size of double-tube
tire has a corresponding size of inner tube, an inner tube

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16 AUTOMOBILE TIRES §11

smaller than thq size intended for a casing can be used in an
emergency. Thus, an inner tube intended for a 3-inch
casing can be used in a SJ-inch or even a 4-inch casing of the
same tread diameter, provided the tube is of good rubber.
It is not advisable, however, to make a practice of using an
inner tube smaller than is intended for a casing. An inner
tube larger than the proper size for a casing can also be used
temporarily, as in an emergency. A tube that is too large,
however, wrinkles in the casing and is liable to chafe through
quickly or crack at the short bends of the wrinkles.

25. Desiicnatlon of Tire Sizes. — The size of an
American pneumatic tire is designated by first giving, in
inches, its outside diameter over the tread and then the
diameter of the circle that closely conforms to the outside
cross-section of the tire. Thus, when speaking of a 32" X 4"
tire, it means that the tire has an outside diameter of 32 inches
and that a circle 4 inches in diameter will approximate the
external outline of the cross-section.

Tires are made in certain standard sizes that are agreed on
by tire makers; these sizes are changed, however, from time
to time, as occasion demands. Tires are also made to suit
the wheel rims of foreign cars, in which case their size is
stated in millimeters. The millimeter is TsW of the meter,
the length of the meter being 39.37 inches, nearly.

26. Pepmanent Tire Treads. — The tread of tires is
made in various contours, the most common one being the
plain round tread, shown in Figs. 2, 3, and 6. A tire having a
flat tread, as shown in Fig. 5, is believed by many persons to
give more protection against side slip than does a round-tread
tire. The form of tread shown in Fig. 4, in which conical
rubber studs project from the tire, is known as the Bailey
tread; it is also intended to ^ve protection against side slip.
With the same object in view, tire treads are provided by
different tire makers with raised projections of a great variety
of shapes. Permanently attached tire treads are sometimes
made of leather and studded with steel rivets placed in a
manner similar to that shown in Fig. 4.

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«n

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CVBBtOH TIRES

• 1

27, The liability of the pneumatic tire to puncture and
consequent deflation, to rupture of the fabric tinder extraor-
dinary stresses, and to other injuries, has led to the design

Fm. 10

Fjc u

of many fonns of cushion tires, some of which are composed
entirely of soft rubber and some of rubber and fabric.

28, In Fig. 10 is shoAvn a short piece of one form of cush-
ion tire that can be applied to a regular chncher or quick -
detachable clincher rim. To give a cushioning effect, there
is a small circular hole a in the center of the tire; and to per-
mit its ready appHcation to a clincher rim, the base of the
tire is split, as shown
at b.

29. In the cush-
ion tire shown in Fig,
11, the inside contour
resembles that of the
ordinary pneumatic
clincher tire, except
that the tread a is
made very thick.
This tread is sup-
ported at short inter-
vals by blocks b of soft rubber- This type of tire is intended to
take the place of pneumatic clincher and quick-detachable
clincher tires, and for this reason is made to ht the same rims,

222— 3fi

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18 AUTOMOBILE TIRES § 11

30. A solid soft-rubber cushion tire made to fit standard
clincher and quick-detachable rims, is shown in Fig. 12.
This tire has twin treads a. The sides are undercut, as clearly
shown, and the treads are supported by numerous webbings b
placed in a slanting direction. Steel wires c are placed in
the base of the tire at a considerable angle to the sides and
about 1 inch apart. These wires extend under the clinches
of the rim and aid in retaining the tire on the rim.

80L.ID TIRES

31, Fig. 13 shows a form of solid tire that will fit a solid
clincher rim. This tire is provided with rods, or wires, a that
fit under the edge of the clinch. These wires do not run
completely across the tire, but end near the middle of the
rim. It may be noted that this tire is corrugated a short
distance outside of the clinch for the purpose of making it

Pig. 13

more elastic. The tread of the tire is beaded, the middle
bead being much higher, or of larger diameter, measured
from the top to the bottom of the wheel, than the side beads.
The grooving at the sides, together with the inner bead of
larger diameter, tends to soften the running of the tire on
the roadway.

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AUTOMOBILE TIRES

32. A solid tire for a detachable clincher rim is shown
in Fig. 14. In this case, the wires, or rods a embedded in the
base of the tire run across from side to side at right angles
to the side of the tire. The removable clinch b is held in place
by a rod, or large wire, c, that encircles the wheel rim and is
tightened by a tumbuckle d provided with right- and left-
hand screw threads 'to fit on the threaded ends of the retain-
ing rod, or wire. When pulled tight, the retaining rod rests

Pio 14

Fig. 15

partly on the inclined edge of the wheel rim and partly
against the detachable clinch, so as to hold the latter in place.

33, In Fig. 15 is shown a form of solid tire that fits
between rim flanges that have no retaining action other than
to prevent movement of the tire side wise. The tire is held
against the bottom of the wheel rim by means of two cir-
cumferential -wires, or rods, a and b. These wires are tight-
ened by a tumbuckle or some other suitable means, being
drawn down against the cross-rods c that run through the
base of the tire from side to side.

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§11

TIRE MAINTENANCE

INFIJ^.TION OF TIRES

34, Lioads and Air Pressure for Tires. — There
seems to be no very close agreement either among the manu-
facturers or the users of tires as to just what maximum load
a tire should carry or what should be the pressure of inflation.
This condition is probably due to the fact that tires, other-
wise normally of the same size, are made of different thicknesses
by tire makers, and also that the most suitable inflation pres-
sure depends to some extent on the nature of the road over
which the car is run. It is always safe to assume, however,
that a tire will not show appreciable bulging between the
wheel rim and the roadway if it is properly inflated. In any

case, it is not possi-
ble to formulate a
general statement as
to just how slight,
according to actual
measurement, this
bulging should be.

A thin, flexible
- tire will naturally
.bulge more than a
heavy, stiff one, pro-
vided both are in-
flated to the same pressure. Again, there is a difference
between the pressures that are most suitable for two tires of
the same tube diameter when one is of larger tread diameter
than the other. The tire on a large wheel can carry a heavier
load than one of the same tube diameter on a smaller wheel.
The lower portion of a wheel with a properly inflated tire
is shown in Fig. 16 (a), and a soft tire, as one not inflated
hard enough is called, is shown in Fig. 16 (6).

35. Tables I and II give the inflation pressures recom-
mended by two prominent manufacturers of tires. The

Fig. 10

same pressure.

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AUTOMOBILE TIRES

maximum loads and air pressures given in Table I, however,
are somewhat higher than are generally reconmiended.

TABLE I
IX>AD AND AIR PRESSURE FOR PNEUMATIC TIRES

Diameter of Tire

Weight on Wheel

Air Pressure in Tire

iQches

Potmds

Pounds per Square Inch

175

225

200

300

400

300

400

Soo

600

500

600

700

800

900

105

600

700

800

900

100

1,000

110

700

800

900

1,000

105

1,100

115

36. If an automobile is run at high speed for any length
of time, the tires will be heated considerably and the air
pressure within them will thus be increased. Although this
increase of pressure does not endanger a new tire of good

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quality, it will do harm to an old tire that has become weak-
ened by long use. It is therefore advisable to reduce the air
pressure in such tires by slightly opening the tire air valve.

37. Inflation of Pneumatic Tires. — Generally
speaking, pneumatic tires may be inflated in three ways:

TABIiB n

LOAD AND AIR PRESSURE FOR PNEUMATIC TIRES

Load for Wheel,

Air Pressure in Tire

Size of Tire

Car Without

Pounds per Square Inch

Inches

Passengers

Pounds

Front Tire

Rear Tire

28X2i

225

28X3

350

28X3i

400

30X34

450

32X34

550

34X34

600

36X34

6so

30X4

5SO

32X4

650

34X4

700

36X4

750

30X44

650

32X44

700

34X44

800

36X44

900

34XS

1,000

36X5

1,000

(1) By means of hand-operated tire air pumps; (2) by means
of engine-driven tire air pumps; and (3) by means of com-
pressed air or carbonic-acid gas contained in storage tanks.

38. Hand-operated tire air pumps are made single-
acting, compressing air on the downward stroke, or double-acting,
compressing the air on both the upward and the downward

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stroke. As a general rule, double-acting tire air pumps com-
press the air in two stages; that is, the air is partly compressed
on the one stroke and fully compressed on the next stroke.
Such pirnips are usually called double-acting compound tire
air pumps.

39. En^rine-driven tire air pumps are, as a general
rule, simply small air compressors of the' single-acting type
that are sold as an accessory to an automobile. They are
intended to relieve the operator of the laborious work of
pumping up tires by
hand.

40. S t o r a iBT e
tanks containing
compressed air are
usually found in all
the better garages in
the large cities.
There have recently
been placed on the
market small storage
tanks for tire infla-
tion that may be car-
ried in the automo-
bile. Such tanks,
when empty, may be
exchanged for full
ones at various sup- Pig. i7

ply depots throughout the country. If cost is no con-
sideration, the use of portable storage tanks is ideal for
ease of inflation. However, since the air or carbonic-acid gas
is stored in the tank under great pressure, extreme care must
be exercised not to inflate the tires too much. It is advisable
always to use a tire pressure gauge when inflating from a
storage tank.

41. Hand -Operated Pumps. — I land -operated tire air
pumps are made in many styles and sizes and at different
prices, the price usually being a good guide to the quality.

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24 AUTOMOBILE TIRES § 11

A slngrle-actin^ tire air pump of simple construc-
tion is shown in section in Fig. 17. It has a barrel a that,
in practice, averages about l\ inches in diameter by 20 inches
in length and is made of steel or brass tubing. This barrel
is threaded at both ends. The upper end has screwed to it
the cap b that guides the piston rod c, and the lower end is
screwed and soldered into the base d. A combined check-
valve and hose nipple e is screwed into the base. The check-
valve in the nipple ^ is a small steel or brass ball. The pump
hose (not shown) is pushed over the grooved part of the
nipple and is then wired or clamped to it. The pump piston
consists of two metal washers / and g, between which is
placed the soft cup-shaped leather washer h. All these wash-
ers are locked to the piston rod c with a nut i. A wooden
handle / is fastened to the upper end of the piston rod, and
a folding extension k is usually placed on the base, to receive
the foot of the operator, which holds the pump while it is
being operated.

42, The operation of the pump shown in Fig. 17 is as fol-
lows: On the upward stroke of the pump, owing to the facts
that the washer / is a loose fit in the barrel a and that the cup
leather h is pliable, the leather collapses slightly and air at
atmospheric pressure enters and fills the barrrel below the
piston. To admit air above the piston, a few small holes
are usually drilled through the cap b, although in some cases
the piston rod is made a loose fit in the cap for this purpose.
On the downward stroke of the piston, the cup leather h
expands at once, and as the stroke continues the air in the
barrel is compressed until its pressure is great enough to lift
the check-valve in e, pass into the hose connecting the pump
to the tire, lift the tire air check, and then pass into the
tire or inner tube.

The successful operation of this type of tire air pump
depends on the condition of the cup leather h, which, when
it becomes hard, may be softened by applying a little cylinder
oil. If the cup leather has become brittle or has worn quite
thin, a new one should be applied.

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AUTOMOBILE TIRES

43 • The cheapest tire air pumps have no check- valves
at all; a better grade has one check- valve, as that shown in

Fig. 17. Some tire pumps do not
depend on the collapsing of the cup
leather for admitting air to the bar-
rel, but are fitted with an inwardly
opening air-admission valve. Such
^rg™ii a valve is of doubtful value, as the

i aj^ppp slightest speck of dirt lodging on its

seat will greatly reduce the pressure
capacity of the pump.

44. A typical double-acting
eompound tire pump is shown in
section in Fig. 18. It consists of a
stationary outer barrel a ; a movable
inner barrel 6, to which is fastened
a handle ; and a standpipe c through
which the air is delivered into the
hose d and thence through the tire air
valve into the tire. At the top of the
outer barrel, the inner barrel b passes
through a stuflfingbox that is packed
with a cup leather. The lower part
of the inner barrel carries a piston e
packed with a cup leather and has a
cup-leather-packed stuffingbox / to
make an air-tight joint against the
standpipe c. Fitted to the upper
end of the standpipe is a down-
wardly opening ball check-valve that
is held to its seat by means of a
light helical spring. There is also a
piston g fitted with a cup leather at
the upper end of the standpipe.

45. The operation of the tire
Fig. 18 pump shown in Fig. 18 is as follows:

On the upward stroke of the inner barrel, the air in the

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26 AUTOMOBILE TIRES § 11

annular space between the inner and outer barrel passes
through holes, as /t, directly above the piston e into the top
of the inner barrel and past the cup leather of the piston g.
Since the capacity of the barrel b is much less than that of
the annular space between the inner and outer barrel, the air
is compressed to some extent in the inner barrel when the
upward stroke is ended. On the downward stroke, the cup
leather in the piston g expands against the inner barrel, making
an air-tight joint, and the continuation of the downward stroke
further compresses the air in the inner barrel imtil the pressure
is high enough to unseat both the check-valve at the head of
the standpipe and the tire air check- valve. While this com-
pression of air is going on in the upper part of the inner
barrel, the annular space between the inner and outer
barrel is filling with air at atmospheric pressure that enters
past the cup-leather packing of the piston e. At the same
time, the part of the inner barrel below the piston g also
fills with air at atmospheric pressure that enters past the
cup leather of the stuffingbox /. A few small holes i are
drilled through the outer barrel at its lower end in order
to admit air.

The successful operation of this type of tire pump depends
on the condition of the cup leathers, which must be soft and
pliable.

46. Tire Pumps Fitted With Gauges. — There are
on the market tire air pumps that have a pressure gauge
incorporated to indicate the pressure within the tire. When
such a pump is used, the hose connection to the tire air valve
must be constructed so that the tire air check-valve can be
pushed and held off its seat. If this kind of a connection is
not used, the pressure gauge will register the pressure to
which the pump compresses air, instead of the pressure
existing in the tire.

Tire air pumps are also made with a relief attachment in
the form of a small safety valve. With air pumps of this
kind, the tire cannot be pumped to a pressure higher than
that for which the relief attachment is adjusted.

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47. Pump Connectioiis to Tire Air Valves. — In

Fig. 19 are shown two common types of air-pump connec-
tions. The one shown in (a) has the outer casing a threaded
internally to fit the outside thread at the end of Schrader
valve stems. A fiber washer b makes a tight joint against the
end of the valve stem and also against the end of the air
barrel c, to which the hose leading to the source of air supply
is attached. Owing to the construction, the outer casing a
and its locknut d can turn freely on the air barrel, so that the
hose will remain sta-
tionary while attach-
ing or detaching the
connection to the tire
valve stem.

The form of connec-
tion shown in (b) car-
ries the hose, attached
to the nipple a, at right
angles to the tire valve
stem. The connector fc
is threaded at c to fit
the inside thread at
the end of Schrader
valve stems. A small
screw d passes through
the center of the con-
nector b. When this is screwed in, it opens the air check-
valve of the tire valve stem, thus adapting this connection
to tire pumps fitted with a pressure gauge. ' It can be
obtained without a central screw, however.

(a)

48, While the Schrader valve stem is today the standard
device used on Alperican inner tubes, there are in use many
foreign inner tubes having tire air valves that differ from the
Schrader valve stem. The foreign valve stems mostly used
are the Michelin and the English Dunlop.

To permit the same air hose to be attached to any one of
the three tire valve stems mentioned, the form of connection

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§11

shown in Fig. 20 has been placed on the market. In this type
of connection, the casing a is threaded internally to fit the
outside thread of the Michelin tire valve stem ; the adapter b
is threaded externally to fit the casing a, and internally to fit

Fig. 20

the outside thread of the English Dunlop tire valve stem;
and the adapter c is threaded at one end to fit the internal
thread of the adapter fc, and at the other end to fit the
internal thread at the end of the Schrader tire- valve stem.

49. Tire Pressure Gaugres. — Since insufficient infla-
tion is the most prolific source of tire troubles, and since

only an expert can tell
by observation or by
feeling a tire whether
or not it is properly in-
flated, a tire pressure
gauge should be used
not only when inflating
tires, but also for peri-
odically testing the in-
flation pressure.

50. There are sev-
eral reliable tire pressure
gauges on the market.
One type of gauge is shown separately in Fig. 21, and in
Fig. 22 this same gauge is shown attached to a tire valve
and 'pump. Referring to Fig. 21, the knurled nut a,
threaded inside to fit the outside thread of Schrader valve
stems, is used for connecting the gauge to the tire-valve
stem. The hose from the inflating pump is attached to
the lower middle part of the gauge after the cap c, which
is the same as that used on the valve stem of the tire,

Fio. 21

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AUTOMOBILE TIRES

is removed. By screwing in the knurled nut b after the
gauge has been attached to the tire valve, the small air
valve in the valve stem of the tire is forced from its
seat. The air valve, which then operates as a check-
valve, is in the part of the gauge immediately above the

Fig. 22

cap c. An indicating hand moves over the dial e in the
cylindrical part of the gauge shown at the left-h^nd side.
The dial is graduated to indicate the air pressure in pounds
per square inch.

Schrader tire valves that have a pressure-indicating device
incorporated in the stem may also be obtained.

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§11

TIRE PROTECTORS AND ANTISKID DEVICES

51. Detacliable Tire Protectors. — Ever since the
advent of the pneumatic tire, inventors have been devising
means of protecting it from puncture and at the same time
f'endering it less liable to side slip. In some cases, the devices
have assumed the form of permanent tire treads ; in other cases,
they have taken the form of detachable protectors that are
made in various styles and attached to the tire in a variety

of ways.

A typical detacliable tire

protector is shown in Fig. 23.

This protector consists of an end-

Fio. 23

Pig. 24

less three-ply leather band that is shaped to fit the tread of a
tire and has loops on both edges that receive an endless
crimped wire ring. The tread of the protector is studded with
hardened-steel rivets, so as to get a good grip on the road.
The protector is applied while the tire is deflated and is
intended to be held in place by friction when the tire is
inflated.

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§ 11 AUTOMOBILE TIRES 31

Another type of tire protector is made up of a series of
steel plates linked together. This type of protector is fast-
ened to the wheel rim by means of hooks. Although tire
protectors undoubtedly reduce the liability of puncture and
skidding, they slightly reduce the resilience of the tire and
the speed of the automobile.

52. Antiskid Devices. — In addition to the detach-
able tire protectors, there are many devices that prevent tires
from skidding, but do not protect them from puncture.
These are known as antiskid devices and are generally
in the form of a chain that may be easily detached. A rope
wrapped around the tire and wheel rim will answer fairly

Fig. 25

well as an antiskid device, but this material is seldom used
for this purpose because it will wear out in a very short time.
The rope should not be smaller than J inch in diameter, even
for a very light car. Rope 1 inch in diameter is about the
proper size.

53, In Fig. 24 is shown one form of antiskid tire cliain

in place on a pneumatic tire. This type of chain has been
used extensively and has given entire satisfaction. The com-
plete chain consists of two circumferential chains, one of which
is shown at a. These chains pass around the wheel just out-
side the rim, and are connected together by numerous cross-
chains that pass over the tread of the tire. The ends of the
circumferential chains are fastened together by means of

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very simple fasteners, as shown at b, one of which is provided
in each chain. Both fasteners lie between the same pair of
cross-chains. To put the chain in place, the wheel is jacked
up or the chain is stretched out on the ground, or floor

either in front of or behind the
wheel, and the wheel run on it.
The chain can then be brought
over the wheel and fastened in
place. To remove the chain,
the fasteners are opened and
the chain permitted to drop to
the ground, after which the
wheel is run from it.

54, In Fig. 25 is shown an
antiskid tire chain that is very
similar to the one just described.
The chief difference between
the chains is that the cross-
chains in Fig. 25 are provided
with swivels and are made in
the form of a coiled spring in the
part that bears directly on the
tread of the tire.

55. In the tire chain shown
in Fig. 26, the cross-chains run
zigzag from side to side of the
tire. This type of chain is
claimed to have the advantage
of resisting side slip more effect-
ively than tire chains in which

Fio. 26 the cross-chains run in the direc-

tion of those shown in Figs. 24 and 25. The latter chains,
however, do not permit much side slip to occur.

Tire chains should be examined frequently for sharp edges
that are liable to cut into the tire.

56. Mud HookH. —If an automobile is running on very
wet and muddy roads that are not macadamized, the tire

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chains sometimes do not give sufficient grip to drive the car,
in which event the driving wheels spin ground and the chains
dig into the roadway until the axle or some other part of the
car rests on it.

For running on extremely soft mud roads, a mud liook of
the form shown in Fig. 27 will be found very useful. When
properly placed, this type of mud hook projects far enough
from the tire to get a good grip on the mud. It is advisable
to put at least four hooks on each driving wheel, placing them
at equal distances around the wheel. If only one mud hook
is used on each wheel, as is sometimes recommended, it will
grip the road until the rotation of the wheel lifts it from the
roadway. If the engine is then pulling hard and the clutch

Pig. 27

Fig. 28

is in full engagement, as is the ordinary condition of operation
under the circumstances, the driving wheels will spin around
until the hooks, one on each driving wheel, come into contact
with the roadway again. This will suddenly stop the rotation
of the wheels and cause excessive stresses on the transmission
system, especially if the clutch is one that holds very tight
when in full engagement. The use of four mud hooks on
each wheel will prevent spinning to a great extent and thus
prevent any great stresses on the engine.

The mud hook shown in Fig. 28 is used on a solid-rubber
tire. It can be bolted on more rigidly than can the hook
used on a pneumatic tire, because allowance does not have
to be made for a soft, or deflated, tire.

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34 AUTOMOBILE TIRES § 11

TIRE DETERIORATION

TIRB DETERIORATION THROUGH IMPROPER INFLATION

57. If a tire is not sufficiently inflated to keep it nearly
round when carrying the weight of the car and the passengers,
it is subject to rapid wear both alongside the bead at the
rim of the wheel, called rim cutting, and throughout the body
of the tire. The excessive bending of a tire that is not fully
inflated has a tendency to work the rubber loose from the
fabric and also to cause excessive heating. Even a well-
inflated tire when run at high speed will become extremely
hot. This condition, of course, is more noticeable in hot
weather than in cold.

Fio. 29

If a tire is extremely soft on account of complete or nearly
complete deflation, it flattens at the bottom where it rests
on the roadway, taking a form similar to that shown in
Fig. 29. All the load is then practically carried by the clinch
of the rim or by the retaining rings or flanges, as the case
may be. The result is that the casing is injured by rim cutting
where the clinch or retaining rings bear on it, and the inner
tube may be cut through in places where it is pressed together
just over the clinch or retaining rings. In addition to this,
the heads of the tire lugs in a plain clincher type, as well as
the valve stem end inside the rubber tube, are liable to be
injured, especially if the roadway is very uneven or rocky.

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AUTOMOBILE TIRES

A tire that has become deflated on account of leakage at
the valve, a puncture, or abrasion should never be run. If
no spare tire is available, the rim may be wrapped with rope
or the car may even be run on the bare wheel rim. While
this may spoil the rim, wheel rims are very cheap in com-
parison to tires.

58. It frequently happens that a tire becomes soft on
account of leakage through the air valve and also past the
cap that screws on the valve stem. A test for such leakage
can be made by immersing the end of the valve stem in
water contained in a glass or some other vessel, as illustrated
in Fig. 30. A little saliva placed on the end of the valve stem
will indicate a leak in the air
valve after the cap is removed
from the stem. If leakage
occurs when the cap is in
place, it is of course an indi-
cation that both the valve
and the cap leak. The repair
of either one of these parts
will generally stop the leak.

A leak through the cap of
the valve stem is almost in-
variably due to deterioration
of the small rubbe^r disk pack-
ing in the cap, the disks being cut through or wrinkled on
account of screwing the cap into place. The simplest remedy
for such a leak is to use a new packing disk in the cap. In
the absence of spare rubber disks, one may be cut either from
a piece of old inner tube or from a rubber patch. If none
of these is at hand, a piece of thin leather covered over with
tallow, thick grease, or even rubber cement can be used.
There is apt to be some difficulty in removing the cap after
rubber cement has been applied to the leather disk used
in it, and for this reason it should be removed and cleaned
with gasoline as soon as a suitable disk can be secured and
applied.

Fig. 30

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36 AUTOMOBILE TIRES § 11

About the only satisfactory remedy for a leaky tire air
check- valve is to replace' it with a complete new one. Air
check-valves are so inexpensive that it is about as cheap to
put in a new one as it is to purchase and carry any of the
extra rubber parts. About the only rubber part that can be
removed from the air valve and replaced by a new one is the

cone-shaped piece of
rubber that fits against
the end of the valve
stem to make an air-
tight joint. It is prac-
tically impossible to
renew the rubber valve
Fig. 31 Seat Satisfactorily.

59, The tool shown in Fig. 31 is intended for smoothing
and dressing up battered valve stems of inner tubes. The
tap a is used for cleaning up the thread inside the tubular
valve stem; the die b for recutting the outside thread on the
valve stem ; and the facing cutter c for smoothing off the end
of the valve stem where the rubber packing disk presses
against it. The tubular part above c slips freely over the end
of the valve stem to hold the tool in place, when smoothing the
end of the stem. The slotted end d is used to remove the
small air valve from the hollow valve stem and to screw
the valve into it.

MISCELI^ANEOUS CAUSES OF TIRE FAII-URE

60. Tire Wear Througli Improper Driving?. -^Either

skidding the wheels on a dry road by a too powerful applica-
tion of the brakes or causing the wheels to spin by starting
the car too suddenly, is extremely injurious to the tires,
because the abrasion of the tires against the road cuts and
tears away the tread of the shoe. If the brakes are applied
so hard as to prevent the wheel from turning when the car
is traveling at considerable speed, the heat due to the sliding
of the tire on the road will melt the rubber, and the destruc-
tion of the tire will then be exceedingly rapid.

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§ 11 AUTOMOBILE TIRES 37

Turning a comer at high speed causes an excessive side
pressure on the tires. This, of course, has a tendency to tear
the bead loose from the other portion of the tire. The side
pressure may be sufficient to pull the tire from the rim, to
bend the axle, or to break the wheel. Sharp comers should
be turned at slow speed.

61. PulUniHr lioose of Tire Fabric. — A tire shoe
sometimes fails because the fabric pulls loose along the out-
side of the shoe just above the angle between the bead and
the main body of the tire. When the fabric thus pulls loose
a large blow-out of the inner tube generally follows. Unless
closely looked for, defects of this kind are sometimes difficult
to locate, because as soon as the tire is deflated the torn part
of the fabric will spring back against the body of the tire.
The fault can be readily detected by bending the bead of the
tire down by hand while the tire is off the wheel.

62. Chafing: of Inner Tube. — Chafing of the inner
tube is a frequent source of tire trouble. The chafing ulti-
mately rubs a hole completely through the tube, so that it
becomes deflated. The best, and probably the only, way to
prevent a tube from chafing is to use a liberal quantity of some
such substance as talcum powder, French chalk, or powdered
soapstone. The inner tube should fit the shoe properly;
under no condition should it be too large.

63. Blisters. — Blisters, which frequently form on the
tire shoe, are due to various causes. If a tire is faulty, the
kneading action created by rolling over the road sometimes
works the outer coating of rubber loose from the outer layer of
fabric. Another cause of a blister is a cut through the outer
coating of rubber. Sand and mud work in through this cut
and gradually tear the rubber from the fabric. A blister
formed in this manner is always solid because it is filled with
mud and sand. Sometimes a blister is caused by a puncture
in the inner tube. Thus, the escaping air passes through the
shoe imtil it reaches the outer covering of rubber and then
raises a blister. A blister of this kind, however, is soft.

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38 AUTOMOBILE TIRES § 11

Probably the best thing to do in case of an air blister is to
make a very small puncture through the outer layer of rubber
so that the air can escape. Blisters on a tire shoe cannot be
remedied very well outside of a tire-repair shop.

64, Additional Causes of Undue Tire Wear.

Aside from the various natural causes of tire deterioration,
such as the legitimate wear and tear due to contact with the
road, the rotting of the rubber and fabric due to age, and
the puncture of the casings and tubes by nails and sharp
stones, there are several other causes that may produce a
rapid wear of tires.

Permitting tires to stand on an oil-soaked floor will cause
the rubber to deteriorate rapidly, because oil has the effect
of rotting rubber. Letting a car stand for months unused
on inflated tires will stretch the fabric of the tires locally;
the car should be placed on props when laid up. Improper
alinement of the wheels, especially of the front wheels, is a
prolific source of undue tire wear, because then the tires,
instead of rolling over the road, will roll and slide at the same
time. Improper rear- wheel alinement is practically confined
to cars having a solid rear axle, and can always be traced to
a bent axle.

PRESERVATION OF TIRES IN STORAGE

65. If an automobile is to be laid up for some time, say
a week or so, it is an excellent plan to take the weight off the
tires by putting the machine on four blocks or jacks; in fact,
many owners do this every time they come in from a run.
In this way, the fabric of the tires is relieved of local stresses
and the life of the tires is increased. There is no need of
deflating the tires when the machine is laid up for only a
short time.

If an automobile is to be laid up for a long time, say for the
winter, it is advisable to remove the tires and inner tubes
from the rims. The casings should then be thoroughly
cleaned and carefully examined both inside and outside, and
all needed repairs made at a properly equipped tire-repair

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§ 11 AUTOMOBILE TIRES 39

establishment, unless, of course, the operator has the facilities
and is capable of making the repairs himself. After removing
all rust and dents, the rims should be painted. The tires
may then be replaced on the rims and slightly inflated. The
weight should be taken off the tires by placing four blocks
or jacks under the axles ; also, the place in which the machine
is stored should be dry and not subject to extremes of
temperature.

If a machine must be stored in a damp or a very hot or very
cold place for a long time, it is advisable to remove all tires to
a dry place that has a fairly even temperature. It is well also
not to expose them to direct sunlight.

The greatest enemies of tires and tubes in storage are
intense light, exposure to heat in excess of 75° F., and
dampness. Guarding against these by selecting a proper
place for storage will obviously prolong the life of the tires.

Inner tubes are stored best when slightly inflated, using
just enough air in them to retain their circular form. If
they are folded, cracks are liable to develop in the folds of
old tubes.

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40 AUTOMOBILE TIRES § 11

TIRE REPAIRS

ROADSIDE TIRE REPAIRS

TIRE TOOLS

66. Tire Irons. — Several tools are required to remove
and replace a regular clincher tire with rapidity and ease.

For tires up to, say, 3i

gJJ^jjj|^ ^» ",. . /^. ^Q inches in cross- section,

a pair of tools of the form

^ ^ a.r g -^ shown in Fig. 32 or a

pair of tools of the form
^^""'^^ shown in Fig. 33 may

be used. Both tools are called tire Irons. The tool shown
in Fig. 33 consists of a handle a and tapering blade b with
rounded comers. This tool is sometimes called a tire
prodder.

In the absence of regular tire iroiis, the two halves of a
broken spring leaf make an excellent substitute. Care should
be taken, however, to round the edges with a fine file or by
grinding, so that there will be no sharp edge to cut the tire
or tube.

67. Detaching Tool. — Although the largest tires can
be handled with a pair of tire prodders, or tire irons, the
labor of detaching and attaching tires can be lightened by

the aid of various other

I tire tools. Thus, if the
casing of a clincher tire
i? very stiff or adheres
^°^ to the wheel rim so

tightly at the bead that the ordinary tire prodder cannot be
inserted between the bead and the clinch of the rim without

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AUTOMOBILE TIRES

great difficulty, a detaching tool of the form shown in
Fig. 34 (a) can be used to force the shoe loose from the rim.
The handle, or hand grip, a has two arms, one of which, as 6,
extends outwards and toward the left, as shown, and carries
at the end a wooden roller c that bears against the spoke d
of the wheel when the tool is in use. The arm b is offset to

clear the spoke. The other arm e of the handle has passing
through it a push piece / that bears against the casing just
outside the bead. When the handle a is pulled away from
the wheel, the pusher / forces the bead out of the clinch of the
wheel rim. Notches on the under side of the pusher / make
the tool adjustable for tires of different sizes.

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42 AUTOMOBILE TIRES § 11

The method of inserting a tire prodder by the aid of this
type of detaching tool is illustrated in Fig. 34 (6). As shown,
the detaching tool is used to force the bead of the tire out of
the clinch. The hand grip of the detacher can be supported
by one's knee while inserting the prodder. Each tire clamp
should be pushed in while working near it, so that the clamp
stem will not be bent by. pressure of the tire against it.

68. Continental Tire Tool. — In Fig. 35 is shown
what is known in the trade as the Continental tire tool,

together with the method of
applying it to force the bead
of a tire away from the rim
to permit insertion of the
tire irons.

69. Tire Fork.— Ordi-
narily, one of the hardest
parts of the work in removing
a clincher tire or replacing it
is the lifting of the shoe to
^G- ^ permit the removal or inser-

tion of the tire lugs and the inner-tube valve stem. This task
is rendered comparatively easy, however, if a properly shaped
lever is at hand. There are many tools for this purpose on
the market, a very convenient one being the tire fork
shown in Fig. 36 (a) . The method of applying the tire fork
while removing an inner-tube valve stem from the wheel is
shown in Fig. 36 (b).

70. Miscellaneous Tire Tools. — Another tire tool that
is very convenient for pulling the edge of the tire casing
aside or away from the wheel rim is shown in Fig. 37. The
general form of the tool is shown in view (a), and the method
of applying it, in view (b). As will be seen, the slightly
forked end of the tool rests on the bent-in clincher flange of
the wheel rim. The hooks are caught over the free edge
of the tire shoe, so as to lift it up as the handle of the tool is
pushed away from the operator when the tool is grasped as
indicated in (b).

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71. Fig. 38 shows another style of tool used for the same
purpose as the one shown in Fig. 37. In this tool the end

Fio. 36

opposite the hand grip is left straight instead of being curved
down to catch the wheel rim. The handle bar is generally

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made of a flat piece of metal. When used, the short end

Fig. 37

extending beyond the hooks bears against the tire shoe, but
does not touch the wheel rim. In a tool of this nature, the

^s.^JH-^^^l^

Fig. 38

end that presses against the tire should be rounded, so that it
will not indent or cut into the tire.

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§ 11 AUTOMOBILE TIRES 45

HANDLING OF CLINCHER TIRES

72. Removing the Inner Tube. — One of the most
important things to bear in mind when removing or replacing a
tire is that the inner tube must be handled with great care.
This tube is made of rubber without any strengthening fabric,
and may therefore be easily ptmctured, cut, or torn either
by the tools used or by some of the parts that attach the outer
shoe to the rim of the wheel. Care must also be taken that
the inner tube is not left pinched between any of the clamps,
between the air valve and the outer shoe of the tire, or between
the different parts of the outer shoe. The tools used for
removing and replacing should never have sharp edges or
comers, because they would be liable to injure both the inner
tube and the shoe.

The ordinary clincher tire used on a solid wheel rim prob-
ably requires more skill and care for its removal and replace-
ment than any other form of tire. The method of handling
a clincher tire will therefore be given in detail, for if a person
can successfully deal with this form of tire, there is slight
question regarding his ability to handle any of the others
that are used on the rims with detachable parts.

73. In order to remove a tire, first jack up the wheel so
as to relieve the tire of its load ; then deflate the tire, if defla-
tion has not already occurred, as on account of a puncture
or a leak. To deflate a tire, remove the dust cap from the
valve stem, which, except in some detachable rims, projects
inwards from the rim toward the center of the wheel, and
then press in the end of the small solid valve stem that
appears in the middle of the stem. This valve stem can be
pressed in with a match, a toothpick, or the end of the dust
cap. When the air valve is thus pressed in, the air is allowed
to escape from the tube.

Next, partly unscrew the large nut from the large tubular
stem of the valve, and push the stem in through the wheel
rim. If the stem sticks in the wheel rim, it can be forced in
by pressing a solid wrench against the face of the nut. The

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§11

wrench should be large enough to span the tube without
injuring its screw thread. Remove the nut completely, and
push the stem in as far as possible. Loosen all the nuts on
the clamps that hold the tire in place. The nuts should be
run out to the extreme end of the threaded stems of the
clamps. Press the lugs, or clamps, inwards in the same man-
ner as was done with the valve, so as to free them from the
tire casing. A clamp sometimes sticks so that in order to
press it in a tire tool or some similar device will have to be
used." It may even be necessary to tap lightly against the
bolt of the clamp with a piece of wood or the tire tool. If
the latter is used, it should always be seen that the nut, if

not of the cap-shaped
type, is out far enough
to prevent the tire tool
from striking and injur-
ing the threaded end of
the clamp stem.

Next, insert the thin
point of one of the tire
prodders between the
tire and one edge of the
rim, as illustrated in
Fig. 39. This can gen-
erally be done easily
with a soft tire by pushing the tire over with the hand, as
shown in the figure, or with the foot. In case no tool such
as that illustrated in Figs. 34 and 36 is at hand and the tire
sticks too tightly to allow the insertion of the prodder tire
irons, then a piece of wood shaped to conform to the con-
tour of the shoe just outside the wheel rim, together with a
hammer, can be used to loosen the tire. The method of
using the hammer and tool is the simple one of laying the
block of wood against the side of the shoe and striking the
block with the hammer. The block should, of course, be
amply rounded at the end, so as not to injure the tire.

Next, insert both prodders under the bead of the tire on the
side of the wheel opposite the valve of the inner tube. The

Fig. 39

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AUTOMOBILE TIRES

first trial may be made with the tools about 1 foot apart.
Bring the handles of the tools toward the hub of the wheel
so as to pry the bead out of the rim, as shown in Fig. 40. If
the tools are not too far apart, all the bead between the tools
will be drawn out completely over the rim so as to remain
out when the tools are removed. If the bead is not thus
drawn out, the tools should be brought nearer together and
the operation repeated. Sometimes the tire is so stiff that
it will not remain out of the rim after the tools are removed.
In such a case, one of the tools can be held by one's knee
or foot, so as to keep the bead out, and the other tool
worked along by hand away from the first tool until enough
of the bead is removed to remain out of its own accord. .
The remainder of the
bead can then be
worked off with one
of the tools. Some-
times a soft flexible
tire can be pulled
out of the rim by '
hand after the first ,'
portion is pried out
by the tools.

After removing Fig. 4o

one side of the tire from the rim, grasp the edge of the
tire with one hand at the point farthest from the valve
stem of the inner tube, and pull the tire out from the
rim far enough to insert the other hand to pull out the
inner tube. The inner tube should be removed carefully
on account of its weakness. If it sticks to the casing,
it should not be pulled very hard. The tube sometimes
adheres tightly to the casing on account of having been
heated by fast running, or because some cement on a patch
has been allowed to get between them. If the inner tube
sticks so tightly that it cannot be safely pulled out, it can
be loosened with a little gasoline. The tube should be
removed as soon as possible after the gasoline has been
put in, so that the latter will not have time to act suffi-

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§11

ciently on the rubber to injure it seriously. The gasoline
will generally leave the tube somewhat sticky. After all
the inner tube except the portion just at the valve stem has
been removed, the two tire prodders can be inserted
as far as possible imder the shoe, one tool on each side of
the valve stem and between the casing and inner tube.
The outer ends or handles of the tools can then be brought
together as in Fig. 41, and the tire lifted up with one hand
on the tools while the valve stem is removed from the rim

Fig. 41

with the other hand. A tool of the form shown in Figs. 36,
37, or 38, will be found much more convenient for this pur-
pose than two tire prodders, especially if the tires are large*

74, A good plan in case the puncture can be located before
the inner tube is completely removed from the shoe is to mark
the tube where it is punctured and then inspect the shoe in
the neighborhood corresponding to the puncture in the tube
for the purpose of locating a tack or nail that may have caused

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§ 11 AUTOMOBILE TIRES 49

the trouble. This inspection can be made by rubbing the
hand around the inside of the shoe. If this is not done,
another tube that is put into the shoe will be immediately
punctured by the tack or nail still remaining in the shoe.
If a nail or a piece of wire is found sticking through the
casing for some distance, the tube should be inspected for
two holes, opposite each other, caused by the nail piercing
both sides of the tube.

A small hole can be located by inflating the tube and then
immersing it in water. However, the tube should not be
inflated enough to stretch it much; if inflated too much it
will suddenly expand at one point and is liable to burst if not
caught quickly in the hand. It may be necessary to stretch
the tube by hand in order to open the hole so that air will
escape.

Before putting in another tube, the inside of the shoe should
be cleaned so as to remove all loose dirt and sand. Both the
tube and the inside of the shoe should be liberally coated with
talcum powder, French chalk, or powdered soapstone before
putting them together, and the inner tube should be deflated
as nearly as possible. This can be done by rolling up the tube,
beginning at the part farthest from the air valve, which must
be either pressed down during the operation or removed in
order to let the air escape.

75. Benioving: a Clincher Casing: Prom Rim. — If the

casing, or shoe, of a clincher tire is to be completely removed
from the wheel, the tire clamps, provided any are used, must
be taken out after removing the inner tube. The clamps can
be removed after prying the tire away from the rim, as when
removing the valve stem of the inner tube. The complete
removal of the shoe is then generally easily accomplished.

76. Care of Rims. — If a tire that has been in place for
some time is removed, it will be found that the rim is more
or less rusted. It should therefore be seen that the rim is
cleaned and smoothed before putting the tire on again. The
rust can be removed by scraping. Especial care must be
taken to see that the clincher part of the rim, into which the

222—27

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50 AUTOMOBILE TIRES § 11

shoe bead fits, is thoroughly clean. When rust collects under
the clinch, it may prevent the bead from going entirely into
the proper position. After the rust is scraped off, the rim
should be smoothed with a fine file. Emery cloth can also
be used to advantage for smoothing the rim.

The edge of the rim that bears against the tire just outside
of the bead should be carefully smoothed so that it will not
cut into the tire. When the rim is very rough in the middle,
and the form of the shoe is such that the inner tube bears
against this portion of the rim, a piece of ordinary cotton tape
may be wrapped circumferentially around the rim so that
the inner tube will bear against it. The end of the tape can
be secured with a small quantity of rubber cement.

A protective coating, such as paint, is sometimes put on
the rim to prevent it from rusting. This coating should be
of such nature that it will not adhere to the shoe after the tire
has become heated from running. A mixture of beeswax
and graphite is also sometimes used. The frictional grip of
the tire on the rim will not be so great after it has been
painted in this manner as when the metal is left bare.

77. Replacing: a Shoe. — A new shoe and inner tube
can be put on in two ways. One way is to put the tube inside
the casing first, and then put them both on together; the other
way is to put one bead of the casing on the rim first, and then
put the inner tube in place, as when putting a new tube in a
tire that has had only one side removed from the wheel.
It is probably better for the novice to adopt the latter method,
because there is less danger of injuring the inner tube than
when both parts are put on together. Putting the first bead
of the shoe on the rim is generally a simple operation. Some
new shoes are painted inside with talcum or some other
similar substance, so that it may not be necessary to put in
any talcum powder, French chalk, or powdered soapstone
when putting in the tube.

Some plain clincher shoes are provided with an internal
flap, which is simply an extension of one of the inner edges
of the shoe. This flap is intended to prevent the inner tube

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AUTOMOBILE TIRES

from coming into contact with the rim. When putting the
tire on the rim, the edge with the flap should be put on first.

78. Inserting^ an Inner Tube. — To insert an inner
tube, the tire lugs being in place, first lift the shoe at the
opening in the rim through which the air valve passes in the
same manner that it was lifted to remove the valve of the old
tube. Then insert the valve of a new tube in the hole through
the rim, and work in the remainder of the tube by hand.

Fig. 42

taking care not to twist it. As soon as the inner tube has
been put in the shoe it should be inflated slightly. This
inflation should be only enough to give the tube its circular
form as nearly as possible. Then force the bead back into the
rim, using the tools in the manner illustrated in Fig. 42.
The tool must not be inserted far enough to catch and pinch
the inner tube. Each tire clamp should be pushed from the
wheel center outwards while forcing the tire in place near it;
also, the air valve should be similarly pressed outwards while
working near it.

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The tire can sometimes be replaced more rapidly and easily
by sitting down opposite the wheel and pressing against the
side of the tire with both feet, at the same time striking the
inner side of the bead of the tire lightly with the hammer.
The blows of the hammer, together with the pressure of the
feet, cause the bead to jump in over the rim. This work must
naturally be done at the bottom of the wheel, and the wheel
must be rotated as the tire goes into place. The hammer
should not have sharp edges.

Fio. 43

Fio. 44

After the tire has been put in place, a good plan is to pull
it back and forth sidewise in order to work the bead com-
pletely in under the rim. This work may be aided by fre-
quently striking the tread of the tire with one of the tire tools
or the hammer.

As soon as the tire is in place, each clamp and valve tube
should be pushed in to see that the tube is not caught tmder
it. The clamps can then be tightened lightly, and the inner
tube inflated up to about full pressure. It is advisable

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AUTOMOBILE TIRES

to push the clamps and valve tube in during the early part
of the inflation, in order to make sure that the inner tube
is not pinched by them.

If the valve stem and clamp stems work as freely through
their holes in the rim as they should, there will be a cushion-
like resistance to pushing them outwards, and they will spring
back to position of their own accord. Next, before the tire is
completely inflated, tighten
the clamps and the nut on
the valve stem almost as
tight as they are to be fin-
ally, and then finish inflating
the tire and tighten all nuts i
as they should be. The!

Pig. 46 Fio. 46

clamps and valve tube should not be drawn down very
hard, because excessive tightening will probably break them.

79. Pincliiiig: Inner Tnbes. — Some of the ways in
which an inner tube is liable to become pinched, and hence
injured, or a tire lug or valve stem caught when proper care
is not exercised in putting a tire in place are illustrated in
Figs. 43 to 46.

In Fig. 43, the inner tube is shown caught under one side
of the head of the tire lug. If an inner tube is left in this

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54 AUTOMOBILE TIRES § 11

position, it will surely be ruptured. The inner tube will
spring out from under the lug, however, when the latter is
pushed up, provided it is inflated to such an extent that it
will keep its cylindrical form.

In Fig. 44, one side of the tire lug is shown caught under
the edge of the shoe. In such cases, the edge of the shoe
must be removed from the bead and the lug pushed up before
the tire can be put on completely.

In Fig. 45, a portion of the inner tube is shown caught
under the edge of the tire on the side that is on the rim, while
the other edge of the tire is free from the rim. This con-
dition may occur when the shoe and the inner tube are put
together before placing them on the wheel rim ; or, it may be
the result of improper handling of the tire tools, especially
the prodders, by means of which the tube may be pushed
under the shoe. It is not likely to occur, however, if the
tube is properly inflated.

In Fig. 46, a portion of the inner tube is shown pinched
under the valve stem in the same manner that it is caught
in Fig. 43. The remedy is the same in ^ach case. As has
already been stated, the operator should always pass his hand
around the inner tube after it has been inserted and is slightly
inflated, in order to straighten it out before putting the
second bead of the tire shoe into place.

ROADSIDE 1NN£R-TUB£ REPAIRS

80. Although it is not generally advisable to attempt to
repair a ptmcture of the inner tube on the road, it may
be done in case of necessity. Tire patches for such repairs
are obtainable in the market, and they are put on with proper
repair cement. The patch should be large enough to extend
1 inch or more beyond the hole on all sides.

Before putting on a patch, the portion of tire that is to be
patched should be carefully cleaned by rubbing fine emery
cloth or sandpaper over it. Sometimes gasoline is first used
to clean the tube in this locality. If it is used, the cleaning
should be done very quickly, so that the gasoline will evapo-

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§ 11 AUTOMOBILE TIRES 55

rate and pass off before it has a chance to act on the rubber
to any noticeable extent. Some tire makers and repairers
object to the use of gasoline for this purpose. No water or
other moisture should be allowed on the parts to be repaired.

After cleaning, the rubber cement is spread over both the
patch and the part of the tube that is to be repaired. The
cement should be allowed to dry until it becomes thick in
consistency, but still sticky when one's finger is applied to it.
Some cements require an application of acid or so-called
acid-cure solution and do not have to dry to the same extent.

The patch is then laid on, but care must be taken not to
enclose a bubble of air tmder it. Probably as good a way
as any is first to put down
one comer of the patch while
holding the rest up from the
tube, and then to bring the
patch down gradually, as would
be done if it were rolled down
with a cylindrical tool. After
the patch is in place, it should
be held down hard against the
tube. This can be done by
laying the tube on a flat siuf ace
and then placing a weight on
the top of the patch, or a clamp
like that shown in Fig. 47 may
be used to hold the patch and ^*°' ^^

the tube together. If the clamp is used, one of its inner
faces should be covered with thick felt or thick cloth so as
not to injure the tube. The length of time required for the
cement to set depends on the kind that is used. Ordinary
cement will probably require at least 10 minutes.

A patch put on in this manner will not hold nearly so well
as a patch that is properly vulcanized, because the heat due
to running the car at high speed will soften the cement and
the bending of the tire will aid in working the patch loose.
However, a patch put on with cement will hold better in
cold weather than in warm weather.

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ROADSIDE REPAIRS TO CASINGS

81. Inside Casing Patches. — If the shoe is cut
through so as to make a hole of considerable size, it will be

Fig. 48

necessary to put some sort of patch on the inside of the shoe
so as to prevent the inner tube from blowing out through
the hole. Patches for this purpose, known as Inner-slioe
patches, or sleeves, can be obtained in many styles.
They are usually made of rubber-filled fabric.

One style of patch is shown separately in Fig. 48 (a), and
in place in the tire casing in Fig. 48 (6). Another form of
inner repair sleeve is shown in place in Fig. 49. This patch
is provided on each side with a sheet-metal clip that goes
between the rim and the part of the casing that rests on the
portion of the wheel rim that lies between the clinches or
retaining rings. Another form of inside patch, made entirely
of rubber fabric, is shaped at the edges to fit into the clinches
of the rim. It is sometimes difficult to get the tire in place

when such a patch is
applied, on accoxmt of
the increased thickness
at the bead of the tire.
There is also on the
market a rubber fabric
^°'^^ in sheets that can be

cut to form and placed inside the shoe. This fabric is gen-
erally coated with gummy rubber and is called friction fabric.
The rubber is a cement that will adhere to the shoe when the
sleeve is put in place.

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§ 11 AUTOMOBILE TIRES 57

82. Outside Casing: Protectors. — If the cut in the shoe
is so large that there is danger of the shoe tearing open when
inflated, it is advisable to put an outside protector patch
over the tire. Protector patches, also called manchons, made
for this purpose, are on the market. One form of patch is
provided with eyelets and a lace, so that it can be laced into
place, as illustrated in Fig. 50. Probably the best protector
is made of rubber and woven fabric, in a manner somewhat
similar to the tire shoe. Other materials, especially leather,
are also used extensively for this purpose.

A fairly good protector patch for temporary use can be made
from a section of an old tire shoe. The beads should be cut
off if the old tire is of the clincher type. Holes can then be
pimched for the lacing.

If the cut in the casing is comparatively small and deep,
as when made by a small piece of glass, it should be probed
with the blunt end of
some small instrument
as soon as it is discov-
ered, in order to ascer-
tain whether or not the
glass still remains in it.
Frequently, a small
piece of glass will embed ^^^- ^

itself in the rubber near the surface of the tread as the wheel
passes over it, and then gradually work its way through the
shoe and puncture the inner tube as the wheel travels along
the road. The glass should be removed immediately.

83. Cuts and Blisters. — Cuts of any kind, as well as
blisters, on the tire shoe should be repaired at t^e earliest
possible moment. If the cut is left open, a sand blister or a
mud boil is almost certain to form. Although it is hardly
possible to make a durable repair of a cut while on the road,
it can- be remedied to some extent. If the cut is very
small, it can be temporarily repaired by filling it with rubber
cement and then binding a piece of adhesive tape around
the tire over it. The patched tire should not be run on for

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about a half hour or more. If the cut is rather large and deep,
it may be protected by forcing a piece of rubber patch into it
and then cementing this patch in place. After the cement
has set, the patch can be trimmed down smooth with the
surface of the tire.

PROPER METHOD OP CARRYING INNER TUBES

84. In order to carry an inner tube so that it will not
be abraded and cut, it should be fully deflated and then
closey folded or rolled and put into a casing, or box. It can,
of course, be deflated by rolling it up. The successive steps of

^,. :.-<*=iSJ^

Fig. 51

folding a tire into a bundle are illustrated in Fig. 51. It is
best to cover the valve stem with an ordinary rubber finger
cap, or with a cap of some other material, such as chamois
skin or cloth. Two of the views of the illustration show the
valve stem covered in this manner. An oilcloth bag makes a
suitable covering for the entire tube after it is folded. The
tube should by no means be carried loose among tools, nor
should it be placed where oil or gasoline can get on it. .

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§ 11 AUTOMOBILE TIRES 59

VUIiCANIZED TIRE REPAIRS

VULCANIZING PROCESS

85. The process of vulcanizing rubber, as already referred
to in connection with patching inner tubes and shoes, consists
in heating the rubber to a temperature sufficient to make it
change from either the gummy or the plastic state, as the
composition may be, to the condition that is found in a new
casing. When vulcanizing, extreme care must be taken not
to raise the temperature of the rubber above a certain
maximum. If the rubber is overheated, it will become weak,
will lose its elasticity, and will be almost certain to crack
when bent short, as in the case of a tire shoe when in use
on a rough or stony road.

The heat for the vulcanizing apparatus is generally
supplied by steam, electricity, or gas. The temperature to
which the rubber is raised by the vulcanizer should probably
never exceed 250^ to 275° F. The temperature of the vul-
canizer should naturally be somewhat higher than that
required in the rubber for vulcanizing it, because there is
some loss of heat between the vulcanizer and the tube or
casing. It is advisable to lay an inner tube on a piece of soft
material, such as thick felt, in order that it may have an even
contact or pressure against the vulcanizer, especially when
putting on a large patch.

86. On account of the great danger of injuring the rubber
tube by overheating, a person learning to use a vulcanizer
should experiment on some worthless tubing. He should
take care not to overheat the tubing at the first trials, and
should then increase the temperature in successive trials
until he finds the lowest temperature at which the rubber is
vulcanized so that the patch will hold in place firmly and
cannot be pulled off by hand, as when put on with tire cement
but not vulcanized. The length of time required to vulcanize
an inner tube after the vulcanizer has become thoroughly

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60 AUTOMOBILE TIRES § 11

heated varies with the thickness of both the tube and the
patch, but it does not generally require more than 15 minutes.
It is necessary to bring the temperature up to a certain mark
before vulcanizing will occur. Therefore, there is no need
of trying to produce a successful piece of work by using a low
temperature and continuing the process for a long period.
Dealers in automobile rubber supplies can generally furnish
sheet rubber of the proper nature for making patches that
are to be vulcanized.

As in the case of patches that are not vulcanized, the patch
should be carefully put on and pressed down, so that the patch
and the tube will be in intimate contact before vulcanizing.
Sometimes a roller tool consisting of a comparatively small
round-edged roller in the end of a handle is used for this pur-
pose, being rolled back and forth across the patch.

87. The material used for stopping holes and cuts in the
outer shoe is generally plastic rubber of about the same con-
sistency as thin putty. If the hole to be repaired is large,
it may be partly filled with elastic rubber, put in together
with the plastic rubber. The vulcanizing is then carried on
in the same manner as for an inner tube. Generally, however,
a slightly higher temperature of the vulcanizer is necessary
when dealing with the tire shoe, because, on account of its
larger size, it has the greater tendency to cool. Sometimes
it is also necessary to continue the process somewhat longer,
chiefly for the reason just mentioned.

REPAIR OF CUTS, BL.OW-OUT8, AND TREADS

88. A rim-cut tire shoe can often be repaired in such a
manner by an expert tire repairman that it will give long
service, provided the tire is otherwise good. Repair is made
by vulcanizing strips of rubber fabric over the bead and up
from the bead on both the inside and the outside of the casing.
However, on account of the increased thickness due to the
repair, it is sometimes difficult to get the bead into the clinch.

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§ 11 AUTOMOBILE TIRES 61

89. A cut of moderate size or a blow-out extending
through the casing can sometimes be patched by separating
the different layers of tire fabric from each other for some
distance around the hole and then inserting a suitably shaped
piece of rubber between each pair of adjacent plies of tire
fabric. The process consists in gradually working the patch
pieces in between the layers of the tire. Cement or plastic
rubber composition is put between the patches and the tire
fabric, and the outer portion of the hole is filled with rubber
composition so as to produce a smooth surface at the patch.
The tire is then vulcanized at the place where the repair is
made.

90, When a tire shoe has been in use until the rubber
tread has worn off enough ior the fabric to show in places,
the tire shoe, if the fabric is still in good condition, can often
be repaired to advantage by retreading it.

Two methods of retreading a casing are in use. The pre-
liminary work in both methods is the same. It consists in
removing all the old tread from the casing, cleaning the
exposed fabric of all dirt and washing it with gasoline, and
then applying vulcanizing cement to the fabric. When this
cement has dried to the proper consistency, a so-called tread
battdy made in the right shape and of rubber in a semivulcan-
ized state, as regularly furnished for this purpose by tire
manufacturers, is applied.

The casing, in one process, is then enclosed in a cast-iron
mold of the required shape and entirely surrounding the tire,
a circular spring or other type of metal core being placed inside
the casing. The mold with the enclosed casing is then placed
in a steam kettle and heated by steam until the rubber is
vulcanized. A tread produced as just explained is called a
molded tread.

In the other method, an air bag, which is simply a heavy
inner tube made expressly for repair work of this kind, is
placed inside the casing, and the semivulcanized tread band
is secured to the shoe by tightly wrapping long strips of muslin
around the casing. The shoe is then placed in a steam kettle

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and vulcanized in direct contact with the steam ; a tread thus
produced is called a liand->vrappecl tread.
. Many tire repainnen prefer to build up new treads from
sheet rubber instead of using a semi vulcanized tread band.

91. The repair of large cuts, blow-outs, and beads, as
well as the retreading of tires, should be entrusted only to a
properly equipped tire-repair shop or to tire manufacturers.
As a general rule, however, manufacturers will repair only
tires of their own make.

PORTABLE VUL.CANIZERS

92. Portable Electric Vulcanlzer. — A small port-
able electric vulcanlzer, together with the rheostat
for regulating the electric current, is shown in position

in Fig. 52. The vul-
canizer a is supplied
with electric current
through the double
conductor b. The
current coming to the
vulcanizer passes
through the rheostat
c, the resistance of
which can be regu-
lated by hand to give
the amount of current
that produces, by
passing through the
resistance coils of the
vulcanizer, the re-
quired temperature
Fio- 52 for the vulcanizing

process. As shown in the illustration, the vulcanizer is lying
on the inner tire tube d.

A thermometer is provided to indicate the temperature of
the interior of the vulcanizer. The advice of the manufac-
turer of the apparatus as to what temperature should be

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AUTOMOBILE TIRES

used when vulcanizing should be followed as closely as
possible.

93. Steam-Heated Vulcanlzer. — In Fig. 53 is shown
a steam-lieated portable vulcanlzer attached to the
tire shoe in position for vulcanizing. At the upper part is a
reservoir, or tank a, that holds the water. . One side of this
tank presses against the tire shoe. At the lower part of the
vulcanizer is a lamp i? that furnishes heat for boiling the
water in the vulcanizer
proper. A thermometer c
is inserted into the steam
and water contained by the
vulcanizer, so as to indi-
cate the temperature. If
a steam-pressure gauge is
used instead of a thermom-
eter, it is customary to use
a steam pressure of about
40 pounds per square inch
by the gauge for inner
tubes, and slightly more
for the tire shoes. A steam
pressure of 40 pounds per
square inch corresponds to
a temperature of about
285° F.

Fig. 53

94, Gas-Heated Vul-
canlzer. — In Fig. 54 (a),
a portable g^as-lieated vulcanlzer that uses acetylene gas
is shown in place on a tire casing. A vulcanizer operated in
this manner has the advantage that it can be used wherever
the car may be, provided the acetylene gas, which is ordinarily
used for headlights, is at hand. In Fig. 54 (6) the vulcanizer
is shown in place on an inner tube that is partly removed
from the shoe. A thermometer a indicates the temperature
of the vulcanizer.

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95. Shape of Vulcanizing Surfaces. — The surface
of the vulcanizer that comes into contact with the parts to
be vulcanized is generally made flat when intended for use
on inner tubes and similar parts, but when intended for use

on tire shoes, it has a curved surface suitable to fit closely
upon the shoe. When a shoe is to be vulcanized in place on
the wheel, the tire should be partly deflated, so that it will
make contact with the entire surface of the vulcanizer.

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INDEX

Note.— All items in this index refer first to the section (see the Preface) and then
to the paire of the section. Thus. "Air cooHnff, H, pl9." means that air cooling will
be found on pasre 19 of section 4.

Antiskid devices, fill, p31.

devices. Tire protectors and. {11. p28.

tire chain. {11. p31.
Armature. {8, p3.

Action of, {8. p4.

and commutators. {8. p7.

core and winding. Magneto. {8. p23.

Magneto with stationary. {8. p55.

or keeper. {6. pl2.

Shuttle-wound magneto. {8, p28.

winding. Magneto with single. {8, p45.

winding. Magneto with double. {8. p40.
Artificial magnets. {6. pi 2.
Atwater-Kcnt spark generator. {7. pi 6.
Automatic engine governors, {4. p36.

engine starters, {4. p31.

grease cup. {10, p33.
Automobile carbureters. Requirements for,
{5. p20.

conical-roUer bearings. {10. pO.

-engine auxiliaries. {4. pi .

oils. {10. p34.

tires. {11, pi.
Auxiliaries. Automobile-engine. {4, pi.
Auxiliary compression-feed gasoline tank,
{5, pl6.

spark gap. {7. pO.

Accumulator, Paure type of lead, {6, p32.

Plants type of lead, {6. p32.

plates, or grids of lead. {6, p31.
Accumulators, {6, p21.

Lead, {6. p31.
Acid-cure solution, {11, p55.
Adjustment and regulation of carbureters.

{5, p51.
Air cooling, {4, pl9.

inlet controlled by throttle. Carbureters
with, {5, p43.

intake pipes for carbureters. Hot- and cold-,
{5. P47.

Mixtures of gasoline and, {5, pi 2.

pressure for tires. Loads and, {11. p20.

Proportions of gasoline and, {5, pi 4.

pumps. Hand-operated tire, {11, p22.

pump, Sins^e-acting tire, {11. p24.

xmmps. Double-acting compound tire,
{11. pp23, 25.

xmmps, Engine-driven tire, {11, p23.

storage tanks for tire inflation. Compressed-,
{11. p23.

valves. Pump connections to tire, {11, p27.

valve, Tire, {11, p9.
Alcohol and water mixtures. Table of freezing
point of, {4, pi 7.

as a fuel. {5, p9.

Denatured, {5, p9.

Ethyl, or grain, {5, plO.

Methyl, or wood. {5. plO.
Alternating-current conversion for battery
charging. {6. p40.

current. Definition of. {6. plO.
Ammeter, {6, p7.

Ammeters and voltmeters, {7, p28.
Ampere, volt, and ohm. {6, p6.
Annular ball bearing, {10, pl2.
Anti-freezing solutions, {4, pi 6.

222—30""" • vii

Baflle-plate type of spray valve, {5. p44.
Bailey tire tread. {11. pi 6.
Ball bearing. Annular. {10. pi 2.

bearing. Two- point contact. {10, pl2.

bearings. {10, pll.

bearings, Cup-and-cone. {10. pll.

thrust bearings. {10. pl3.

thrust bearings. Coiled-roller and. {10. pl4.
Band clutch, {0. pi 6.
Batteries, Charging of storage, {6, p34.

Dry, {6. p21.

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INDEX

Batteries— (Continued)

Poiir-cylinder jump-spark. Ignition with,
57.P44.

Primary, (6, pp21 22.

Secondary, or storage, (6, pp21, 30.

when not in use Recharging of storage.
&6. p38.
Battery. Capacity of storage. (6. p34.

charging. Alternating-current conversion
for. 56. p40.

connections. $6. p24.

connections. Multiple, or parallel. {6. p26.

connections. Parallel-series, |6. p28.

connections. Series-, {6. p24.

Definition of electric. (6, p20.

Direct-current generator and storage.
S8. pl6.

"Ploated on the Line," Storage, §8, pl6.

Laying up of storage. {6. p39.

Reversed connections in parallel, {6. p27.

Reversed connections in series. {6, p26.

-switch connection. §6, p29.
Baimi^ hydrometer, §5, p6.
Baum^'s readings for liqjiids lighter than
water, Table of specific gravities corre-
sponding to. {5. p7.
Beads of tire casing, {11, p4.
Bearing, Annular ball, $10. pl2.

Ball thrust, filO. pi 3.

Conical-roUcr thrust, 510. p8.

Cup-and-cone ball. {10. pll.

Cylindrical roller. {10, pG.

Pixed type, {10. pi 6.

Floating-axle type. {10. pi 6.

Lining of, {10. p2.

metals. White. {10. p3.

Plain, {10, pi.

Thrust, {10, p6.

Two-point contact ball, {10, pl2.
Bearings, Automobile conical-roller, {10, pO.

Ball. {10, pll.

Coiled-roller. {10. p9.

Coiled-roller and ball thrust. {10. pi 4.

Materials for shaft. {10. p3.

Oil grooves in. {10. p4.

Oil scoops for crankpin. {10, p4.

Roller, {10, p6.

Roller thrust, {10, p6.

SoUd-roUer, {10, p8.

Steering-knuckle and wheel-hub, {10, pl5.

Types of, {10, pi.
Bevel-gear differential, {9. p45.

-roller friction transmission, {9. p36.
Blisters on tire casing. Cuts and, {11. p57.

on tire shoe, {11, p37.
Blow-outs, and treads. Repair of cuts.
{11.P60.

Bolted-on tire. Pisk. {11, p5.

Bolts, Tire lugs, clamps, clips, or security,

{11. P4.
Bosch high-tension magneto. {8. p55.
Box of bearing. Definition of. {10. pi
Brake device, Impact. {6. p40.

Emergency. {9. p55.

equalixers, {9, p57.

Service. {9. p55.
Brakes. Contracting. {9. p55.

Double-acting. {9. p5d.

Dragging of, {9. p5d.

Expanding. {9, p55.

Single-acting. {9. p56.
Brass. Composition of, ilO, p3.
Breaker strips of tire, {11, p5.
Broken, or open. Circuit. {6. plO.
Bronze, Composition of, {10. p3.

Cables, Insulated copper, {7, p26.
Calcium-chloride-and-water mixtures, Table

of freezing point of, {4, pl8.
Cam, Snap {7, p2.
Capacity of storage battery, {6. p34.
Carburation, Pefinition of, {5, p2.

Principles of, {5. pi.
Carbureter, Compensating springless, {5, p42.

connections, {5, p49.

construction, {5. p28.

Definition of, {5, pp2. 19.

Priming the, {5, p90.

regulation and adjustment, {5, p51.
Carbureters, Advantage of spray. {5, p21.

Classification of. {5, pl9.

Compensating, {5. p31.

Filtering. {6. pi 9.

Float-feed spray, {5. p28.

Gravity-feed, or floatless, {5, p46.

Hot- and cold-air intake pipes for, {5, p47.

Objections to surface and filtering, {5. p20.

Principles of spray, {5, p22.

Requirements for automobile, {5, p20.

Spray. {5. pl9.

Surface, {5. pl9.

with air inlet controlled by throttle. {5. p43.
Casing, Beads of tire, {11, p4.

Cuts and blisters pn tire, {11. p57.

from rim, Removing a clincher, {11, p42.

or shoe. Tire, {11, pi.

patches. Inside, {11. p56.

protector, Outside tire, {U, p67.
Casings, Roadside repairs to tire, {11. p56.
Cell. Resistance and voltage of a. {6. pi 1 .

Voltaic, qr galvanic. {6. pO.
CeUs. Dry. {6, p23.

Wet, {6. p22.

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INDEX

Centrifugal water-drculatmg pumps, {4, pl2.
Chafing of inner tube, fll. i>37.
Chain. Antiskid tire, $11. p31.
Change-speed gear, {9. p20.

-speed gear. Pour-speed and reverse selec-
tive, $9. p25.

-speed gears. Individual-clutch, $9. pp20. 31 .

-speed gears. Planetary, {9. pp20, 32.

-speed gears. Sliding. }9, p20.

-speed mechanism, Horizontal sliding-gear
progressive, (9, p21.
Charge-and-discharge system of magneto
ignition. Condenser, (8, p41.

Definition of, $5, p2.

Definition of electrical, $6, pi.
Charging, Alternating-current conversion for
battery, f 6. p40.

engine starters, {4. p33.

of storage batteries, {6, p34.
Circuit, Broken, or open. S6. plO.

Closed, or comjAete, £6. plO.

Definition of electric. §6, plO.

Divided. §6, pll.

External. $6, plO.

Crotmded, $6, plO.

Internal, {6, plO.

Magnetic, S6, pl4.
Circulating pump. Centrifugal water-, |4, pi 2.

pumps. Water-, $4, pl2.
Circulation, Gear-pump for oil or water,
|4, pl4.

of water in radiators, |4, pi 1 .

pressure gauge, |4, pi 6.
Clamps, clips, or security bolts. Tire lugs,

111. P4.
Clinch of whedrim, §11, p4.
Cliticher casing from rim. Removing a.
ill, p49.

tire. Handling of, fill, p45.

tire. Quick-detachable. (11, p7.

tires. 111. p3.
Clips, or security bolts. Tire lugs, clamps,

§11. P4.
Closed, or comi^ete, circuit, {6, plO.
Qutch. Band, (9. pl6.

Contracting, J9, pi 7.

Expanding, §9. pl7.

Leather-faced cone, 19. p5.

Multiple-cone. {9, pl6.

Multiple-disk friction. §9, p9.

-releasing mechanism, §9. p6.

Reversed cone, {9, p6.
Qutches, Cone, $9, p2.

Contracting and expanding, {9, pl6.

Cork-insert. $9. p9.

Disk. §9. p9.

Materials for friction, S9, pl9.

Clutches — (Continued)

Purpose of, §9, pi.
Coil, High-tension. §6. pA^.

Inductance, {6, p43.

Low-tension, $6, p44.

Magnetizing, or exciting, (6, pl6.

Make-and-break, S6, p43.

Primary, §6. p44.

Primary spark, §6, p43.

Secondary, S6, p44.

Transformer, or non-vibrator induction,
S6 p45.

Two spark plugs with one, §7, p42.

-type magneto, S8, pi.
Coiled -roller and ball thrust bearings, {10, pi 4.

-roller bearings. filO, p9.
Coils, Field magnets and, {8, p9.

Inductance, or kick, |6. p41.

Induction, }6, p43.
Cold -air intake pipes for carbureters, Hot-
and, §5, p47.

weather. Cooling liquids for use in, {4, pi 6.
Combustible mixture. Definition of, {5, p2.
Combtastion, Definition of, $5. p2.

Products of, i5, p3.
Commutators, Armature and, $8, p7.

Distributors, or secondary, |7. pl2.

Timers, or xmmary, §7, plO.
Compensating carbureters. S5. p3I.

or equalizing, gear, §9, p44.

springless carbureters, $5, p42.
Complete circuit. Closed, or. (6, plO.
Compound field winding. §8. pi 2.

tire air pumps. Double-acting. §11, pp23, 25.

-wound dynamo-electric generator, §8, pi 2.
Compressed-air storage tanks for tire infla-
tion, §11, p23.
Compression-feed gasoline tank. Auxiliary,
§5, pl6.

gasoline tanks, {5, pl5.

lubricator. Combined gravity and. J 10. p22.

lubricators. Pressure, or. §10. p22.
Condenser charge-and-discharge system of
magneto ignition. §8, p41.

Electric. §6, p45.

Grounding the. §7. p42.
Conductors and insulators. §6, p2.
Cone clutch. Leather-faced. §9. p5.

clutch. Multiple, §9. pl6.

clutch. Reversed. §9. p6.

clutches, §9, p2.
Conical-roller bearings. Automobile, §10. p8.

-roller thrust bearings. §10. p8.
Connections. Arrangement of steering. §9. p45

Battery. §6. p24.

Battery-switch. §6. p29.

in parallel battery. Reversed. §6, p27.

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INDEX

Connections — (Contintied)

in series battery, Reversed, {6. p26.

Multiple, or parallel, battery. {6. p26.

Parallel-series battery, {6, p28.

Series-battery. $6, p24.

to tire air valves. Pump, ill, p27.
Contact igniter. Low-tension, §7, pi.

-spark system of ignition, {7, pi.

system of ignition, {7, p34.
Continental tire tool, {11. p42.
Contracting and expanding clutches, {9, pi 6.

breaks. {9, p55.

clutch, §9, pl7.
Cooling, Air, §4, pl9.

liquids for use in cold weather, {4, pi 6.

system. Engine-, §4. pi.

system. Water-. §4. p3.

Thermo-siphon system of. {4. p4.
Copper cables. Insulated, §7, p2G.
Core of electromagnet, {6, pi 6.
Cork-insert clutches, {9, p9.
Coupling, Oldham, §9, p42.
Coui^ings. Universal. §9, p39.
Crankpin bearing, Oil scoop for, {10, p4.
Cup-and-cone ball bearings, {lO, pll.
Current, Definition of alternating, {6, plU.

Definition of direct, {6. plO.

Definition of electric. {6. p2.

frequency, $8. p23.

Graphic representation of magneto, {8, p21.

Interrupted primary magneto. {8, p35.

Interrupted short circuit of primary mag-
neto. §8, p40.

interrupter. Vibrator, trembler, or, §6, p49.

Primary, §6, p44.

Secondary, f 6, p44.

Short-circuited primary magneto, f8, p39.
Currents, Eddy, §8, p27.
Cushion tires, §11, ppl. 17.
Cut-outs, Muffler, §4, p27.
Cuts and blisters on tire casing, |11, p57.
Cuts, blow-outs, and treads. Repair of.

ill, p60.
Cylinder oils, {10. p36.

sight-feed gravity oil cup, $10, p21.

Denatured alcohol, f 5. p9.
Density, Magnetic, {6, pi 4.
Depolarization, Polarization and, {6, p21.
Depth gauge. Gasoline tank. |5. pl8.
Detachable, rim. Removable, or, §11, p7.

tire protectors, fll, p30.
Detaching tool. Tire-, fll, p40.
Differential, Bevel-gear, f 9. p45.

gear, J9, p44.

gears, Princifdes of operating. }9, p43.

Differential — (Continued)

Spur-gear, {9. p44.
Direct current, Definition of, §6. plO.

-current generator and storage battery.
»8. pJ6.

-current generator, Elementary, §8, p2.

-current generators. {8. pi.
Direction of the lines of force. §6, pi 4.
Disk clutches. {9. p9.

Distributor. Combined timer and. |7, pi 5.
Distributors, or secondary commutators,

§7. pl2.
Divided circuit, {6, pll.
Double-acting brake, {9. p56.

-acting compound tire air pumps. {11. p23.
Double- tube tires, {11, pi.
Dragging of brakes, §9, p56.
Driving, Tire wear through improper.

Sll. p36.
Dry batteries, {6, p21.

cells, S6, p23.
Dual ignition, $7. p42.
Dunlop tire, $11. p6.

valve stem, English, {11, p27.
Dynamo-electric generator, Compouno-
wound. {8, pi 2.

-electric generator. Shunt-wound. $8, pll.

-electric generators, $8. pi.

•electric generators, S^-excited. {S, pll.

Earth. Definition of, $6, plO.

Eddy currents, $8, p27.

Electric battery. Definition of, §6. p20.

circuit. Definition of, §6. plO.

condenser, S^, p46.

current, §6, p2.

generator. Essential parts of. 58, p3.

generator, Series-woimd, 58. pll.

potential. Definition of, 56, p4.

vulcanizer. Portable, 511. p62.
Electrical charge. Definition of, 56. pi.

units, 56, p6.
Electricity, Definition of, 56, pi.
Electrode, Negative terminal or, 56, plO.

Positive terminal or, 56. plO.
Electrodynamics, 56. p2.
Electrolyte, Definition of, 56. p9
Electromagnet. Core of, 56, pi 6.

Horseshoe, 56, pl8.
Electromagnetic induction, 56, pl8.

induction. Law of, 58, pl9.
Electromagnets, 56. pl6.
Electromotive force, 56. p5.

force. Direction of induced. 58. p2.

force. Intensity of, 58, p3.
Electrostatics, Definition of, 56, p2.

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INDEX

Emergency brake, $9. p55.
Engine-cooling system, §4. pi.

-driven tire air pumps, $11, p23.

governing devices, $4, p34.

governors. Automatic, {4, i>3d.

starters. Automatic, §4* I>31.

starters. Charging, {4, p33.

starters. Hand, {4, p29.

starters. Pressure, §4, p32.

starters. Spring-operated, {4, p31.

starting and governing devices, {4, p29.
^ starting device. Safety, {4, p90.
English Dunlop valve stem, §11, p27.
Equalizers, Brake, {0, p57.
Equalizing gear. Compensating or, {O, p44.
Eth)d, or grain, alcohol, §5, plO.
Exciting, coil. Magnetizing, or, {6, pi 6.
Exhaust gases, §5. p3.

mufflers, {4, p24.
Expanding brakes, {9, p55.

clutch, S9, pl7.

clutches. Contracting and, {9, pl6.
Exidosion, Definition of. §5, pi.
Explosive mixture, Definition of. §5, pi.
External circuit, {6, plO.

Fabric, Friction, §11. I>56.

Pulling loose of tire, §11, p37.
Paure type of lead accumulator, §6, p32.
Field magnet, §8, p3.

Magnetic, §6, pi 4.

magnets and coils, §8, p9.

magnets. Magneto, §8, p28

winding, Compound, §8. pl2.
Filtering carbureters, §5, pl9.

carbureters. Objections to surface and,
§5, p20.
First speed, §9, p22.
Fisk bolted-on tire, §11. p5.
Fixed tyi>e bearing, §10, pl6.
Flame propagation, Rate of, §5. p2.
Flashing point of kerosene, §5, p9.
Float-feed spray carbureters. §5, p28.
"Floated on the Line," Storage battery,

§8, pl6.
Floating-axle type bearing. §10. pi 6.
Floatless, carbureters, Gravity-feed, or,

§5, p46.
Flux, Magnetic, §6, pi 4.
Force, Definition of electromotive, §6, p6.

Direction of electromotive, §8, p2.

Direction of lines of, §6, pi 4.

Intensity of electromotive, §8, p3.

Magnetic lines of, §6. pi 4.

Magnetomotive. §8. plO.

Thermoelectromotive, §6, p6.

Forced -circulation splash system of lubri-
cation, §10, pl8.
Fork, Tire, §11, p42.

Four-cylinder jump-spark ignition with bat-
teries, §7, p44.
-speed and reverse selective change-specJ
gear, §9, p25.
Freezing point of alcohol -and -water mixtures.
Table of, §4, pl7.
point of caldum-chloride-and-water mix-
tures. Table of, §4, pl8.
point of mixtures of glycerine, wood alcohol,
and water. Table of, §4. pi 9.
Frequency, Current, §8, p23.
Friction fabric, §11, p56.
-gear transmission, §9, p35.
gears, §9, p20.

materials for clutches, §9. pl9.
transmission. Bevel-roller, §9, p36.
Pud. Alcohol as a, §5, p9.
Fuels, Vaporization of liquid, §5, pll.

Galvanic, cell. Voltaic, or, §6, p9.
Gap, Auxiliary spark, §7, p9.

Safety spark. §6, p47.

Spark. §7, p5.
Gas-heated portable vulcanizer, §11, p63.
Gases. Exhaust, §.5. p3.
Gasoline. §5, p4.

76-degree, §5, p6.

and air. Mixtures of, §5, pl2.

and air. Proportions of, §5, pi 4.

in tanks. Methods of measuring qtiantity
of, §5, pl8.

Quality of, §5, p5.

Spedfic gravity of, §5, p8.

Stale. §5. p5.

Stove, §5. p6.

supply tank. Reserve, §5. pl7.

supply tanks. Classification of, §5. pi 5.

tank. Auxiliary compression -feed. §5, pl6.

tank depth gauge, §5. pl8

tanks. Compression, §5, pi 5.

tanks, Gravity, §5, pl6.

Testing of. §5. p6.
Gauge, Gasoline tank depth. §5. pl8.

Water-circulation pressure. §4, pi 6.
Gear, Change-speed. §9, p20.

Compensating or equalizing, §9. p44.

Differential. §9, p44.

Four-speed and reverse selective change-
speed, §9. p2r).

-pump for oil or water circulation, §4, pi 4.

Reversible steering, §9. p50.

Reversing, §9, p20.

Screw-and-nut steering. §9, p52.

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INDEX

Gear — (Cootinued)

Worm-and-sector tyi)c of steering, §0, p61.
GeaiB. Friction. {9. p20.

Individual-clutch change-speed, {9, pp20, 31 .

Planetary change-speed. §9. p20; {9. p32.

Principles of operation of differential.
§9. p43.

Reversing position of speed-changing.
89. P24.

Sliding change-speed, §9, p20.

Steering. {9, p49.
Generator and storage battery. Direct-
current, f8, pl2.

Atwater-Kent spark, f7, pl6.

Compound-wound dynamo-dectric. f 8. pl2.

Elementary direct-current, {8. p2.

Elementary magneto, f 8, p23.

Essential parts of electric, $8. p3.

Series- wound electric, §8. pll.

Shunt-wound, dynamo-electric, §8, pll.

Theory of magneto. f8. pi 9.
Generators. Direct-current. §8, pi.

Dynamo-dectric. §8. pi.

Magneto electric. f8. pi.

Self -excited dynamo-dectric, §8, pll.
Glycerine, wood alcohol, and water. Table of

freezing points of mixttues of. f4. pi 9.
Governing devices. Engine, §^ p34.

Devices, Engine starting and, f 4. p29.

Hand, f 4. p34.
Governors, Automatic engine, f 4, p36.
Grain, alcohol. EthyU or, f 5, plO.
Gravity aiyl compression lubricator combined,
f 10. p22.

-feed lubricators. §10, p20.

-feed or floatless carbureters, {5, p46.

Gasoline tanks. f5, pi 6.

oil cup. Cylinder sight-feed. $10. p21.

oil cup. Sight-feed. {10. p20.
Grease cup, Automatic, f 10. p33.

cup. Ratchet, f 10,«p33.

cups, f 10. p32.

cups. Oil and. {10. p31.
Grids of lead accumulator. Plates, or, {6. p31.
Ground. Definition of, §6. plO.
Grounded circuit. }6. plO.
Grounding the condenser, f 7. p42.
Gauge, Tire pressure. §11. p28.
Gauges. Tire pumps fitted with, f 11. p26.

Hand engine starters. §4. p29.

governing, §4, p34.

-operated tire pump, §11, p23.

switches, *§7, p21.
Hess- Bright high-tension magneto, §8, p45.
High-tension coil. §6. p44.

High— (Continued)

-tension magneto, Bosch, §8. p55.

-tension magneto, Hess-Bright. §8. p45.

-tension magneto, Pittsfield, §8, p60.

-tension magneto, U. & H., §8. p49.

-tension magnetos, §8, p42.

-tension system of ignition, Jtmip-spark or.
§7. pi.

•tension ignition system. Sini^e-spark,
§7,p36.
Honeycomb radiator. §4, plO.
Hooks, Mud, §11. p32.

Horizontal sliding-gear p rogre ssi ve change-
speed mechanism, §9, p21.
Horseshoe electromagnet. §6. pl8.
Hot- and cold-air intake pipes for carbur^ers,

§5, p47.
Hoyt voltammeters. §7, p30.
Hydrocarbons. §5, p3.
Hydrometer. Baum^ §6. p6.

Igniter. Low-tension contact, §7, pi.

Make-and-break. §7. p4.
Ignition, Condenser charge-and-discharge
system of magneto, §8, p41.

Contact-spark system of, §7, pi.

Contact system of, §7, p34.

Definition of. §5, p2.

Dual, §7. p42.

High-tension system of, §7, p36

Jump-spark or high-tension system of.
§7, ppl, 36.

Low-tension system of, §7. ppl . 34.

Make-and-break system of. §7. ppl. 34.

system, Individual-cnil, jump-spark. §7. p44.

system. Single-spark high-tension, §7. p36.

system. Six-cylinder, §7, p45.

systems. Dual. §8. p42.

systems. Low-tension magneto, §8, p36

Time of. §o. p2.

Touch-spark system of. §7. ppl. 34.

Two-cylinder engine. §7. p43.

Wipe-spark system of, §7, ppl. 34.

with batteries, Four-c>dinder jump-spark,
§7. p44.
Impact brake device, §6. p49.
Impedance, or inductive resistance. §8. p33.
Individual-clutch change-speed gears. §9.
pp20. 31.

-coH jump-spark ignition system. §7. p44.

•pump lubricator. §10. p25.
Induced electromotive force, §8. p2.
Inductance coil. §6. p43.

or kick, coils. §6. p41.
Induction coil. §6. p43.

coil. Transformer, or non-vibrator. §6, p45.

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INDEX

xui

Induction — (Continued)

Electromagnetic. {6. pl8.

in revolving loop, S^, p20.

Lnw o( electromagnetic, {8, pi 9.

Magnetic, {6, pi 4.
Inductive restifitance. Impedance or, {8, p33.
Inductor type of magneto. §8, p81 .
Inflammation, or exf^osion, Duration of.

56, p2.
Inflation of pneumatic tires. {11, p22.

of tires, {11, p20.

Tire deterioration through improper,
§11. P31.
Inlet controlled by throttle. Carbureters with

air, {5, p43.
Ixmer-shoe patches, or sleeves, f 11, p66.

tube. Chafing of, f 11, p37.

tube for tire, fU, pi.

tube. Inserting an, {11, p51.

tube. Removing the, {11, p45.

-tube repairs. Roadside, {11, p54.

tubes, {11. pl5.

tubes. Pinching, {11, p53.

tubes. Proper method of carrying, {11, p68.
Insulated copper cables. {7, p26
Insulating substances. {6. p3.
Insulators, Conductors and, {6. p2.
Intake pipes for carbureters. Hot- and cold-

air. {5. p47.
Intensity of electromotive force, {8. p3.
Internal circuit, {6, plO.

resistance, {6. p9.
Interrupted primary magneto current, {8. p36.

short circuit of primary magneto current.
{8. p40.
Interruptor, Vibrator, trembler, or current.

{6. p49.
Irons, Tire, {11, p40.

Joints, or couplings, Universal, {9, p39.
Journal, Definition of, {10, pi.
Jump-spark ignition system. Individual-coil,
57.P44.
-spark ignition with batteries, Pour-
cylinder, {7. p44.
-spark, or high-tension, system of ignition.

{7. pi.
-spark system of ignition, {7, p36.

Keeper. Armature* or, {6, pl2.
Kerosene, {5, p8.

Flashing point of, {5. p9.
Kick coil. {6. p43.

coils. Inductance, or, {6, p41
K-W magneto, {8, p33.

Law of electromagnetic induction, {8. pl9.

Ohm's, {6, p7.
Laying up of storage battery, {6. p39.
Lead accumulator. Paure tyi>e of, {6. p32.

accumulator. Plants type of, {6, p32.

accumulator. Plates or grids of. {6. p31.

accumulators. {6. pSl.
Lines of force. Direction of, {6, pi 4,

of force, Magnetic, {6. pl4.
Lining of bearing. {10, p2.
Liquid fuels. Vaporization of, {5, pll.
Loads and air pressure for tires, {11, p20.
Loadstone, {6. pl2.
Low-tension coil. {6, p44.

-tension contact igniter, {7, pi .

-tension magneto-ignition systems, {8. p36.

-tension magnetos. {8. p29.

-tension system of ignition. {7, p34.
Lubricating devices. {10, pi 9.
Lubrication, Definition of, {10. pl7

Porced-circulation si^ash system of,
{10, pl8.

Splash system of, {10, pi 8.
Lubricator. Combined gravity and compres-
sion, {10, p22.

Individual-pump, {10. p25.

Multiple sight-feed gravity. {10. p22.
Lubricators, Comparison of, {10, p30.

Gravity-feed, {10, p20.

Mechanical, {10, p25.

Pressure, or compression, {10. p22.
Lugs, clamps, clips, or security bolts. Tire,
{11. P4.

Tire, {11, pl4.

Magnet, Field, {8, p3.

Neutral region of, {6, pl3.

Poles of, {6, pl3.

Yoke of. {6. pl8.
Magnetic circuit, {6, pl4.

density. {5, pi 4.

field. {6, pi 4.

fiux. {6, pl4.

induction, {6, pi 4.

lines of force, {6. pi 4.
Magnetism, Definition of. {6. pl2.

Residual. {6. pl6; {8. pl2
Magnetite. {6, pl2.

Magnetizing, or exciting, coil, {6. pi 6.
Magneto, armature core, and winding, {8.
p23.

armature. Shuttle- wound. {8, p28.

Bosch high-tension, {8, i>55.

current, Graphic representation of, §8, p21,

current. Interrupted primary, {8, p36.

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XIV

INDEX

Magneto — (Continued)

current. Interrupted short circuit of
primary, §8, p40.

current. Short-circuited primary, {8. p39..

-electric generators, {8. pi.

field magnets, §8, p28.

generator, Elementary, {8, p23.

generator. Theory of, §8, pl9.

Hess-Bright high-tension, §8, p45.

Inductor type of, {8, p31.

ignition. Condenser charge- and -discharge
system of, §8. p41.

ignition system, Low-tension, }8, p36.

K-W, 58. p33.

Pittsfield high-tension. §8. p60.

Remy, §8, p35.

with double armature winding. S8, p49.

with single armature winding, f 8, p45.

with stationary armature. {8. p56.

with stationary winding, {8, p60.

U. & H. high-tension, §8, p49.
Magnetomotive force. (8, plO.
Magnetos. Coil-type. §8, pi.

Non-«ynchronous. (8. p2.
Magnets and coils. Field, §8, p9.

Artificial. §6, pl2.

Low-tension, {8, p28.

Magneto field, 58, p28.

Natural, §6, pl2.

Permanent, §6, pi 2.
Make-and -break coil. |6, p43.

-and-break igniter, |7. p4.

-and -break system of ignition, §7, ppl, 34.
Manchons, §11, p57.
Master vibrator, §6, p52.
Measuring quantity of gasoline in tanks.

Methods of, (5. pi 8.
Mechanical lubricators. }10, p25.
Mechanically fastened tires, §11, p3.
Mercury-vapor rectifying apparatus, §6 p40.
Metals, White bearing. §10, p3.
Methyl, or wood, alcohol, §5, plO.
Micanite. §8. p8.
Michelin valve stem. §11, p27.
Mixture, Definition of combustible, §5, p2.

Definition of explosive, §5, pi.
Mixtures of gasoline and air, §5, pl2.
Molded tread, §11, p61.
Motor generators, §6, p40.
Mud hooks. §11, p32.
Muffler cut-outs, §4, p27.
Mufflers, Construction of. §4. p25.

Exhaust. §4. p24.
Muffling. Purpose of. §4, p24.
Multiple-cone clutch. §9, pl6.

-disk friction clutch, §9, plO.

oiler, §10, p22.

Multiple — (Continued)
or parallel battery connection, §6, p26.
sight-feed gravity lubricator, §10, p22.

Natural magnets. §6, pI2.
Negative terminal or electrode. §6, plO.
Neutral region of magnets. §6. pl3.
Non-synchronous magnetos, §8, p2.
Non-vibrator induction coil. Transformer, or.
§6, p45.

O
Ohm, Ampere, volt, and. §6, p6.
Ohm's law, §6, p7.
Oil and grease cups. §10. p31.

cup. Cylinder sight-feed gravity, §10, p21.

cup. Sight-feed gravity. §10, p20.

cups, §10. p31.

grooves in bearings, §10, p4.

or water circulation. Gear-pump for.
§4. pl4.

scoops for crankpin bearing, §10, p4.
Oiler, Multiple, §10. t^22.

Precision, §10. p29.
Oils. Automobile. §10 p34.

Cylinder. §10. p36.

Grades of. §10, p35.

Properties of, §10, p34.

Testing of, §10, p36.
Oldham coupling, §9. p42.
Open, circuit. Broken, or. §6, plO.

Primary current, §6, p44.

Primary magneto current Interrupted, §8,p36.

magneto current, Interrupted short circuit
of. §8, p40.

magneto current. Short-circuited, §8, p39.

spark coil, §6. p43.
Priming the carbureter, §5, p30.
Principles of spray carbureters. §5. p22.
Prodder, Tire, §11 p40.
Products of combustion. §5. p3.
Progressive change-speed mechanism. Hori-
zontal sliding-gear, §9. p2l.

transmission, §9. pp20, 21.
Protector, Outside tire casing, §11. p56.
Protectors, Detachable tire, §11. p30.
Pump, Centrifugal water-circulating, §4, pi 2.

connections to tire air valves, §11, p27.

for oil or water circulation. Gear-, §4, pi 4.
Parallel liattery connections. Multiple, or,
§6. p26.

battery. Reversed connections in, §6, p27.

-series battery connections, §6, p28.
Patches, Inside casing, §11, p56.

or sleeves. Inner-shoe. §11, p56.

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INDEX

Permanent magnets. 16. pl2.

Pinching inner tubes, ill, p53.

Pipes for carbtireters. Hot- and cold -air

intake, {5, p47.
Pittsfidd high-tension magneto, (8, p50.
Plain bearing, {lO, pi.
Planetary change-speed gears. $0. pp2U. 32.

transmission. Two-speed and reverse,
J9. p32.
Plants type of lead accumiilator, {6, p32.
Plates or grids of lead acctiroulator {6. p31.
Plugs, Spark, §7. p5.
Pneumatic tires, SUt pl-

tires. Inflation of. {11. p22.

tires. Types of, {11, p2.
Polarity of solenoid. {6, pl7.
Polarization and dex)olarization, {6, x^l.
Poles of magnet, {6. pl3.
Positive terminal, or electrode. {6, plO.
Potential. Definition of electric. {6, p4.
Precision oiler, {10, p29.
Pressure engine starters, {4, p32.

for tires. Loads and air, {11. p20.

gauge. Tire. {11, p28.

gauge, Water-circulation. {4, pi 6.

or compression, lubricators. {10, p22.
Primary batteries. {6, pp21. 22.

coil, {6. p44.

commutators. Timers or. {7. plO.
Pump. Hand-operated tire. {11. p23.

lubricator. Individual-. {10. p25.

Single-acting tire air, {11. p24.
Pumps, Double-acting compound tire air.
{11. pp23. 25.

Engine-driven tire air. {11. p23.

fitted with gauges. Tire. {11. p26.

Hand-operated tire air. {11. p22.

Water-circulating, {4, pi 2. ,

Quick-detachable rim. Standard universal.
{11. P6.
-detachable clincher tire, {11. p7.
-detachable tire. Plat-base type. {11. p6.
detachable tires. {11. p3.

Radiator, Honeycomb. {4, plO.
Radiators, Circulation of water in, {4. pll.

Types of. {4, p8.
Ratchet grease cup, {10. p53.
Recharging of storage batteries when not in

use. {6. p38.
Rectifying apparatus, Mercury- vapor, §6, p40.
Regulation and adjustment of carbureters.

{5. p51.
Removably, or detachable, rims, {11, p7.

Remy magneto. {8. p35.

Repair of cuts, blow-outs and treads,

{11. P60.
Repairs. Roadside inner-tube, {ll, p54.

Roadside tire, {11, p40.

to tire casings. Roadside, {11, p56.

Vulcanized tire, {11, p.50.
Reserve gasoline supply tank, {5. pi 7.
Residual magnetism. {6, pi 6; {8. pi 2.
Resistance and voltage of a cell, {6, pi 1 .

Definition of, {6. p4.

Impedance, or inductive. {8, p33.
Reversed cone clutch, {9, p6.

connections in parallel battery. {6. p27.

connections in series battery, {6. p26.
Reversible steering gear. {0. p50.
'Reversing position of speed -changing gears,
{9. p24.

gear, {9, p20.
Roadside inner-tube repairs. {11, p54.

repairs to tire casings. {11. p56.

tire repairs. {11. p40.
Roller and boll thrust bearings. Coiled-
{10, pl4.

bearings. {10. p6.

bearings. Automobile conical-, {10, p9.

bearings, Coiled-, {10, p9.

bearings. Cylindrical-, {10, p6.

thrust bearings, {10, p6.
Rope transmission. {9, p38.
Rim, Clinch of wheel, {11, p4.

cutting of tire, {11, p34.

Removable, or detachable, {11, p7.

Removing a clincher casing from, {11 , p49-

Standard universal quick - detachable,
{11. P6.
Rims, Care of, {11, p49.

Safety spark gap, {6, p47.

engine-starting device, {4, p30.
Scovill valve, {11. pi 2.
Schrader valve. {II. plO.
Screw-and-nut steering gear, {9, p52.
Second speed. {9. p23.
Secondary coil. {6, p44.

commutators. Distributors, or, {7. pl2

current, {6, p44.

or storage batteries, {6. pp21. 30.
Security bolts. Tire lugs, clamps, clips, or,

{11. P4.
Selective change-speed gear, Four-speed and
reverse. {9. p25.

transmission, {9, p20.
Self-excited dynamo-electric generators.
{8. pll.

-induction, {6, p42.

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XVI

INDEX

Series-battery connections. 56, p24.

-battery connections, Parallel. §6, i>28.

battery. Reversed connections in, {6. p26.

-wound electric generator, (8. pll.
Service brake. S9. p55.
Shaft bearings, Materials for. {10. i>3.
Shims. §10. p5.
Shoe. Blisters on tire, §11. p37.

Replacing a tire. §11, p60.

Tire casing, or. §11, pi.
Short-circuited primary magneto current.
§8. p39.

circuit of primary magneto current, Inter-
rupted, §8, p40.
Shtint, Definition of, §6, pll.

-wound dynamo-electric generator, §8, pll.
Shuttle-wound magneto armature. §8, p28.
Sight-feed e^vity lubricator. Multii^e,
§10. p22.

-feed gravity oil cup. §10. p20.

-feed gravity oil cup. Cylinder, §10, p21.
Single-acting brakes, §9. p56.

-acting tire air pumps, §11, p24.
Single-tube tires. §11, pi.
Sizes of tire. Designation of. §11. pl6.
Six-cylinder ignition system. §7, p45.
Sleeves. Inner-shoe patches, or. §11, p56.
Sliding change-speed gears, §9. p20.

-gear progressive change-speed mechanism.
Horizontal. §9, p21.
Snap cam, §7. p2.
Solenoid. Polarity of. §6. pl7.
Solid-roller bearings. §10, p8.

tires. §11. pp2. 18.
Solution. Acid-cure. §11. p55.
Solutions, An ti -freezing, §4, pl6.
Spare wheels. §11. p9.
Spark coil. Primary. §6, p43.

gap. §7. p5.

gap. Auxiliary. §7. p9.

gap. Safety. §6, p47.
Spark generator, Atwater-Kent, §7, pl6.

plugs, §7, p5.

plugs with one coil, Two, §7, p42.
Specific gravities corresponding to Baum^'s
readings for liquids lighter than water,
Table of. §6, p7.

gravity of gasoline. §5, p8.
Speed -changing gears. Reversing position of,
§9. p24.

-changing mechanism. Purpose of, §9, p20.

First, §9, p22.

Second. §9. p23.

Third. §9, p23.
Si^ash system of lubrication. §10, pl8.

system of lubrication, Forced -circulation.
§10. pl8.

Spray carbureters, §5, pl9.

carbureters. Advantage of, §5, p21.

carbiireters. Float-feed. §5, p28.

carbureters. Principles of, §5. p22.

valve. Baffle-plate type of. §5. p44.
Spring-operated engine starter. §4. p31.
Springless carbureter. Compensating, §5, p42.
Spur-gear dilTerential, §9, p44.
Stale gasoline, §5, p5.
Standai^ universal quick-detachable rim,

§11. P6.
Starters, Automatic engine, §4, p31.

Charging engine, §4, p33.

Hand engine, §4, p29.

Pressure engine, §4, p32. -

Spring-operated engine, §4, p31.
Starting and governing devices. Engine,
§4. p29.

device. Safety engine, §4, p30.
Steam-heated portable vulcanizer. §11, p62.
Steering connections. Arrangement of, §9, p46.

gear, ReveraiUe, §9, p50.

gear. Screw -and-nut, §9, p52.

gear. Worm -and -sector type of. §9, p51.

gears, §9, p49.

-knuckle and wheel-hub bearings, §10, pl5.
Storage batteries. Charging of, §6, p34.

batteries. Secondary, or. §6« pp21, 30.

batteries when not in use. Recharging.
§6, p38.

battery. Capacity of. §6. p34.

battery. Direct-current generator and.
§8, pl6.

battery "Floated on the Line," §8, pl6.

battery. Laying up of. §6. p39.

tanks for tire inflation. Compressed-air.
§11. p23.
Stove gasoline. §5. p6.
Strips of tire. Breaker. §11. p5.
Surface and Altering carbureters, Objection
to. §5. p20.

carbureters. §5. pi 9.
Switch connections. Battery-. §6. p29.

Double-throw, two-pole, blade. §7, p26.

Single-throw, two-pole, knife, or blade,
§7. p25.

Two-battery. §7, p23.
Switches. Hand. §7. p2l.

Table of freezing point of alcohol-and-water

mixtures. §4. pl7.
of freezing point of calcium-chloride-and-

water mixtures. §4. pl8.
of freezing point of mixtures of glycerine,

wood alcohol, and water. §4. pl9.

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INDEX

xvn

Table— (Continued)

of loads and air pressure for pneumatic
tires, fill. p20.

of specific gravities corresponding to
Baum^'s readings for liquids lighter than
water, §5, p7.
Tank, Auxiliary compression-feed gasoline,
§5. pl6.

depth gauge. Gasoline, {5, pi 8.

Reserve gasoline supply, {5, pl7.
Tanks. Classification of gasoline supply,
§5, pl5.

Compression gasoline, (5, pl5.

for tire inflation. Compressed-air storage,
§11. p23.

Gravity gasoline, §5, pl6.

Methods of measuring quantities of gaso-
line in, §5. pl8.
Terminal or el^trode. Negative. §6, plO.

or electrode. Positive. {6, plO.
Terminals. Definition of. {6, plO.

Insulated wires and wire. §7. p26.
Testing of gasoline, §5. p6.

of oils. §10. p36.
Thermoelcctromotive force, §6, p6.
Thermo-siphon system of cooling. §4. p4.
Third speed. {9. p23.
Throttle, Carbureters with air inlet controlled

by. 15. p43.
Thrust bearing. {10, p5.

bearing. BaU. §10. pl3.

bearings. Coiled-roUer and ball. §10. pi 4.

bearings, Conical-roller, §10, p8.

bearings. Roller, §10, p6.
Time of ignition, §5. p2.
Timer and distributor combined, §7. pi 5.
Timers, or primary commutators. §7. plO.
Tire air pump, Single-acting. §11. p24.

air pumps. Double-acting compound.
§11. pp23. 25.

air pumps, Engine-driven, §11. p23.

air pumps. Hand-operated, §11, p22.

air valves, §11. pO.

air valves. Pump connections to. §11. p27.

Breaker strips of. §11. p5.

casing. Beads of, §11. p4.

casing. Cuts and blisters on, §11, p57.

casing, or shoe, §11, pi.

casing protectors, Outside, §11. p57.

casings. Roadside repairs to. §11, p56.

chain. Antiskid. §11, p31.

•detaching tool, §11. p40.

deterioration through improper inflation,
§11. p34.

Dunlop, §11. p6.

fabric, Pulling loose of, §11, p37.

failure. Miscellaneous causes of, §11, p36.

Tire — (Continued)

Pisk bolted-on. §11, p5.

Flat-base type quick detachable, §11, p56.

fork, §11, p42.

Handling of clincher, §11, p45.

inflation, Compressed-air storage tank for,
§11. P23.

Inner tube for, §11, pi.

iron, §11. p40.

lugs, §11. pl4.

lugs, clamps, clips, or security bolts.
§11. P4.

pressure gauge. §11, p28.

prodder. §11. p40.

protectors and antiskid devices. §11. p30.

protectors. Detachable, §11. p30.

pump. Hand-operate4, §11. p23.

pumps fitted with gauges, §11, p26.

Quick-detachable clincher. §11, p7.

repairs. Roadside, §11, p40.

repairs, Vulcanized, §11. p59.

Rim cutting of, §11. p34.

shoe, Replacing a. §11. p50.

sites. Designation of, §11. pi 6.

tool. Continental. §11, p42.

tools. Miscellaneous, §11, pp40. 42.

tread, Bailey. §11. pi 6.

tread band. §11. p61.

tread. Hand -wrapped. §11, p62.

tread. Molded. §11. p51.

Tread of. §11. p4.

treads. §11. pl6.

tube, Blisters on. §11. p37.

wear. Additional causes of undue. §11,
p38.

wear through improper driving, §11. p36.
Tires, Clincher, §11, p3.

Cushion, §11, ppl, 17.

Double-tube, §11, pi.

in storage. Preservation of, §11, p38.

Inflation of. §11. p20.

Inflation of pneumatic, §11, p22.

Loads and air pressure for, §11, p20.

Mechanically fastened, §11, p3.

Pneumatic, §11. pi.

Quick-detachable. §11. p3.

Single-tube. §11. pi.

Solid. §11. pp2. 18.

Types of, §11, pi.

Types of pneumatic, §11. p2.
Tool, Continental tire, §11, p42.

Tire-detaching, §11, p40.
Tools, Miscellaneous tire. §11, pp40, 42.
Touch-spark system of ignition. §7, ppl , 34.
Transformer, or non-vibrator induction, coil,

§6. p45.
Transmission, §0, p20.

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XVUI

INDEX

Transmission — (Continued)

Bevel-roller friction, f 9. p36.

Friction-gear, {9, i>35.

Progressive, $9, pp20, 21.

Rope. S9, p36.

Selective, {9, p20.

Two-speed and reverse planetary, {9, p32.
Tread. Bailey tire. |11, pi 6.

band. Tire, §11. p61.

Hand-wrapped tire, {ll. pe2.

Molded tire {H. P61.

of tire. ill. p4.
Treads, Repair of cuts, blow-outs, and,
§11. p6i).

Tire, §11. pl6.
Trembler, or current interruptor. Vibrator,

16. p49.
Tube, Chafing of inner, {11, p37.
' for tire. Inner, §11, pi.

Inserting an inner, {11. p5l.

Removing the inner, {11, p42.
Tubes, Inner, {ll, pl5.

Pinching inner, {11, p53.

Proper method of carrying inner, §11, p67.
Two-battery switch, {7, p23.

-cylinder-engine ignit;on, {7, p43.

U. & H. high-tension magneto, {8. p49.
Units, Electrical. {6. p6.
Universal couplings. {9. p39.

quick-detachable rim. Standard, {11, p6.

Valve, Baffle-plate type of spray. {5, p44.

Schrader, {11. plO.

ScoviU. {11. pl2.

stem. English Dunlop. {11. p27.

stem, Micbelin. {11. p27.
Vaporisation of liquid fuels, {5. pll.
Valves. Pump connections to tire air, {11, p27.

Tire air. {11. p9.
Vibrator. Master. {6. p52.

trembler, or current interruptor. {6. p49.

Volt, and ohm. Ampere. {6, p6.
Voltage of a cell. Resistance and, {6, pi 1 .
Voltaic or galvanic cell. {6, pO.
Voltammetere, §7, p28.

Hoyt, {7. p30.
Voltmeter, {6, p5.

Voltmeters, Ammeters and, {7. p28.
Vulcanized tire repairs, {11, p59.
Vulcaniser. Gas-heated porUble. {11, pG3

PorUble electric, {11. pe2.

Steam-heated portable. {Il,p63.
Vulcanising process, {11, p59.

surfaces. Shape of, §11. p64.

Water-circulating pumps, §4, pl2.

-circulating pumps. Centrifugal, {4. pi 2.

-coc^ng system, {4. p3.

in radiators. Circulation of, {4, pll.
Wet batteries. {6, p21.

ceUs, {6, p22.
Wheel-hub bearings, Steering-knudde and.
{10. pl5.

rim. CUnch of. {11. p4.
Wheels. Spare. {11. p9.
White bearing metals, {10, p3.
Winding, Compound field. {8. pi 2.

Magneto armature core and. {8, p23.

Magneto with double armature. {8. p49

Magneto with single armature. {8. p45.

Magneto with stationary. {8. p60.
Wipe-spark system of ignition, {7. ppl. 34.
Wires and wire terminals. Insulated. {7. p26.
Wood alcohol, glycerine, and water, Table of
freezing point of mixtures of, {4, pi 9.

alcohol. Methyl, or. {6. plO.
Worm-and-sector type of steering gear.

{9. p61.
Wrapped tire tread. Hand-. {11. p62.

Yoke of magnet. {6, pl8.

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